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Ore 
Deposits 


A  DISCUSSION 
RE-PUBLISHED 
FROM  THE 
ENGINEERING 
AND  MINING 
JOURNAL 
NEW  YORK 
MAY,  1903 


SECOND  IMPRESSION. 


NEW  YORK  AND  LONDON: 
THE  ENGINEERING  AND  MINING  JOURNAL. 
1905. 


COPYRIGHT,  1903, 

BY 

THE    ENGINEERING    AND    MINING   JOURNAL 


/  K  Y 


CONTENTS 


Page. 
Review  by  the  Editor 3 

Discussion  by  S.  F.  Emmons i8 

Discussion  by  W.  H.  Weed 20 

Discussion  by  J.  E.  Spurr 30 

Discussion  by  W.  Lindgren 2>^ 

Discussion  by  S.  F.  Emmons 42 

Discussion  by  J.  F.  Kemp 45 

Discussion  by  F.  L.  Ransome 52 

Discussion  by  T.  A.  Rickard S^ 

Discussion  by  C.  R.  Van  Hise 60 

Discussion  by  W.  H.  Weed 63 

Observations  by  C.  W.  Purington 68 

Reply  by  J.  F.  Kemp 91 


A  REVIEW. 

The  discussion  on  ore-deposits  which  appears  in  this 
pamphlet  is  a  reproduction  of  the  views  expressed  before 
the  Geological  Society  of  Washington,  at  two  consecu- 
tive monthly  meetings,  early  in  1903 ;  as  reported  in  the 
Engineering  and  Alining  Journal,  but  it  also  includes 
some  important  corrections  and  amplifications  of  the  ma- 
terial previously  published.  In  a  manner,  timely  and 
suggestive,  it  represents  the  latest  opinions  on  a  subject 
which  is  of  perennial  interest  to  all  those  who  are  en- 
gaged either  in  the  academic  or  the  practical  pursuit  of 
the  ore-bodies  valuable  to  man.  The  discussion  gives 
particular  prominence  to  the  recent  accentuation  of  mag- 
matic  differentiation  as  a  factor  in  the  distribution  of  ores 
in  rocks;  this  is  the  reason  why  the  advocates  of  the 
agency  of  water  as  a  determinative  process  are  not  so 
prominent.  Mr.  Emmons,  Prof.  Van  Hise  and  other 
authoritative  writers  have  indeed  taken  part  in  the  discus- 
sion and  added  largely  to  the  value  of  it ;  but  their  pur- 
pose has  been  evidently  more  to  warn  against  the  exag- 
geration of  a  new  motif  in  the  geologic  drama  than  to 
reiterate  their  own  views  fully  until  the  new  theories  shall 
have  been  further  substantiated. 

The  present  position  of  the  study — it  is  not  yet  an 
exact  science — of  ore-deposits  is  worthy  of  a  brief  review. 
It  is  summaried  herewith  in  words  whose  repetition* 
seems  warranted  as  an  introduction  to  the  discussion  on 
which  the  present  pamphlet  is  based. 

Mining  owes  much  to  geology.  This  debt  will,  let  us 
hope,  be  increased,  for  it  is  an  honorable  obligation. 
Science  justifies  herself  to  the  commercial  world  by  the 
practical  aid  which  she  gives  to  industry.  Even  those 
who  delve  underground  for  the  metals  upon  which  mod- 

^  From  an  article  in  the  Engineering  and  Mining  Journal  of  Jan.  i8,  1902, 
entitled  "Recent  Progress  in  the  Study  of  Ore-Deposits,"  by  T.  A.  Rickard, 

—  3  — 


ern  civilization  depends  are  not  without  the  realization 
that  light  has  come  to  them  in  dark  places. 

Geology  was  not  always  a  friend  to  mining.  In  its  in- 
fancy it  made  wild  statements  which  only  perplexed  an 
exceedingly  venerable  industry.  Even  to  this  day,  in 
certain  quarters,  there  is  an  unspoken  idea  that  the  young 
science  stoops  to  commercialism  when  she  concerns  her- 
self with  matters  which  have  to  do  with  mining.  A  nota- 
ble example  can  be  instanced.  The  Geological  Society  of 
England  was  founded  by  the  fathers  of  modern  geology, 
by  men  whose  names  are  household  words,  and  among  its 
records  will  be  found  the  first  presentation  of  the  very 
foundations  of  the  science  to  which  the  society  is  dedi- 
cated. I  desire  to  emphasize  the  historic  position  and 
the  splendid  work,  continuing  to  this  day,  done  by  the 
men  who  compose  that  honorable  society,  which  repre- 
sents all  that  is  best  in  English  geology ;  but  such  emphasis 
will  also  accentuate  the  extraordinary  fact  that,  both  as  a 
body  and  individually,  English  geologists  have  severely 
abstained  from  developing  that  part  of  their  science  which 
touches  most  directly  upon  mining,  namely,  the  study  of 
ore-deposits.  In  striking  contrast  to  this  neglect  of  a 
most  useful  line  of  enquiry  is  the  attitude  adopted  by  the 
geologists  of  the  United  States,  and  more  particularly  by 
the  organized  corps  of  the  Geological  Survey.  From  its 
very  inception,  under  Mr.  Clarence  King,  the  Survey  has 
given  the  warm  grasp  of  friendship  to  the  miner ;  and 
during  the  past  twenty-five  years  the  distinguished  scien- 
tific men  who  have  done  its  work  have  contributed,  not 
merely  a  few  suggestions  or  iridescent  generalizations,  but 
the  results  of  practical  research  of  the  most  useful  kind, 
which  have  formed  the  basis  for  a  systematic  study  of  ore 
occurrence. 

Besides  its  own  contributions  on  a  subject  of  imme- 
diate economic  importance,  the  Survey,  by  the  separate 
writings  of  certain  of  its  members,  has  given  an  impetus 
to  the  investigations  of  mining  engineers  and  others  who 
have  collected  data  for  the  common  fund  of  ascertained 
fact.  The  American  Institute  of  Mining  Engineers  has 
served  as  a  link  to  bring  together  the  official  and  the  pro- 


—  4  — 


fessional  mining  geologists,  the  meeting  of  men  working 
toward  a  common  purpose  by  diverse  paths  having  been 
facilitated  by  the  fact  that  the  distinguished  secretary  of 
the  Institute  was  once  a  government  official  himself/  and 
is  now  the  dean  of  the  mining  engineering  profession. 

The  results  of  this  co-operation  are  manifest.  The 
literature  of  that  branch  of  geology  which  deals  with  the 
genesis,  structure  and  occurrence  of  ore-deposits  is,  in  its 
modern  aspect,  distinctively  American,  and  this  can  be 
said  without  under-estimating  the  inspiration  given  to  the 
study  of  these  problems  by  the  writings  of  such  men  as 
Posepny,  Vogt,  Beck,  De  Launay  and  other  European 
scientists. 

During  the  past  eighteen  years  the  study  of  ore-de- 
posits, in  this  country,  at  least,  has  received  a  marked 
impetus  on  three  notable  occasions.  These  three  im- 
pulses toward  advancement  are  associated  with  the  names 
of  Emmons,  Posepny,  and  Van  Hise.  In  the  history  of 
economic  geology  the  publication  of  the  Leadville  mono- 
graph' marks  a  red-letter  day.  Of  all  reports  on  the 
geology  of  a  mining  district  this  one  has  had  a  value  more 
directly  measurable  in  dollars  and  cents.  Whatever  it 
may  have  cost,  it  is  not  too  much  to  say  that  the  work  of 
Mr.  Emmons  and  his  assistants  gave  to  Leadville  an  un- 
derground chart  which  has  led  to  the  discovery  of  bodies 
of  ore  valued  at  millions  of  dollars.  And  apart  from  its 
immediate  aid  to  the  mine-captains  of  one  district,  it 
proved  a  most  illuminating  guide  to  the  men  who  opened 
up  the  Aspen,  Rico  and  Ten  Mile  districts  in  Colorado.  As 
a  geological  report  made  by  a  national  survey,  it  marked  a 
striking  advance  in  its  detailed  deciphering  of  the  under- 
ground structure  of  a  very  complicated  region ;  for  how- 
ever interesting  and  suggestive  the  questions  concerning 
the  origin  of  ores  may  be,  there  is  no  doubt  but  that  the 
unraveling  of  the    structural    relations    of  ore-deposits 


miis  refers,  of  course,  to  Dr.  Rossiter  W.  Raymond,  to  whom  the 
mining  industry,  in  its  broadest  sense,  owes  a  debt  which  'it  is  pleasant  to 
remember. 

"Monograph,  XII.  Geology  and  Mining  Industry  of  Leadville,  by  S.  F. 
Emmons.  tJ.  S.  Geological  Survey.  Issued  in  1886.  An  abstract,  which 
stated  Mr.  Emmons'  views  quite  fully,  was  pubKshed  in   1882. 


affords  the  more  immediate  aid  to  the  miner,  and  in  this 
respect  the  Leadville  monograph  is  without  a  peer,  before 
or  since  the  date  of  its  first  distribution  to  the  pubhc. 

Following  up  the  Leadville  monograph,  Mr.  Emmons 
studied  the  neighboring  mining  localities,  and  this  resulted 
in  the  publication  of  several  contributions  to  the  science 
of  ore-deposits.  Among  these  papers  may  be  instanced 
the  essay  entitled  "The  Structural  Relations  of  Ore-De- 
posits,"* because  it  has  proved  extremely  suggestive  to  the 
younger  men  who  were  at  that  time  beginning  to  interest 
themselves  in  this  branch  of  geological  research. 

The  Leadville  work  gave  a  local  application  to  those 
views  upon  the  origin  of  ore-deposits  which  were,  at  that 
time,  in  course  of  ventilation  in  Europe  by  Professor 
Sandberger."  ''Lateral  secretion"  under  various  forms 
and  disguises  became  a  dominant  note  in  the  writings  of 
the  years  between  1883  and  1893.  It  was  a  narrow  inter- 
pretation of  a  very  wide  phenomenon  and,  while  the  chem- 
ical side  of  the  conception  had  a  very  evident  fascination 
for  the  scientist,  it  did  not  recommend  itself  to  those  who 
spend  much  time  underground.  However,  the  objections 
which  this  theory  presented  to  mining  engineers  led  to 
the  gathering  of  a  good  many  new  facts  which  paved  the 
way  for  the  favorable  reception  of  Posepny's  treatise,'  in 
1893.  It  is  an  interesting  coincidence  that  three^  differ- 
ent members  of  the  Institute,  in  the  course  of  papers 
descriptive  of  districts  which  they  had  severally  studied, 
expressed  disagreement  with  the  then  generally  accepted 
lateral  secretion  theory.  Each  thought  his  attack  was  no 
better  than  a  forlorn  hope.  It  was  a  gratifying  surprise 
to  find  afterward  that  the  most  important  contribution  of 
that  year  was  a  very  telling  criticism  of  Sandberger's 
views  by  so  distinguished  an  authority  as  Posepny.  But 
Posepny  did  not  only  destroy,  he  also  built  up,  and  if  his 
structure  bore  signs  of  an  extreme  style  of  intellectual 
architecture,  it  was  none  the  less  a  distinct  improvement 
upon  the  makeshift  which  it  replaced.     It  is  true  he  set  his 

'Vol.  XVI.,  pp.  804-839.  Transactions  of  the  American  Institute  of 
Mining  Engineers. 

^Untersuchungen  uber  Erzgange.     Wiesbaden,  1882. 

8"The  Genesis  of  Ore-Deposits."  Vol.  XXIII.,  pp.  197-369-  Transactions 
American   Institute  of  Mining  Engineers. 

^John  A.  Church,  Arthur  Winslow  and  the  writer. 


advocacy  of  ascending  solutions  against  the  lateral  secre- 
tion theory  of  Sandberger,  but  that  was  the  less  important 
part  of  his  contribution  to  science;  he  brought  out  the 
essential  difference  between  the  waters  above  the  so-called 
water-level  and  those  which  circulate  below  that  horizon, 
and  he  drew  particular  attention  to  the  distinctive  features 
of  the  former,  which  he  then  first  called  by  the  term  now 
generally  in  use — ^namely,  the  vadose  circulation.  While 
the  immediate  result  of  his  famous  treatise  was  to  stir  up 
anew  the  controversy  between  those  who  variously  advo- 
cated the  agency  of  "lateral,"  "ascending"  or  "descend- 
ing" waters  as  primarily  responsible  for  the  deposition  of 
ores,  a  much  better  result  ensued,  since  from  the  discus- 
sion of  the  general  subject  it  became  more  and  more  evi- 
dent that  the  word  "circulation"  was  the  ley  to  the 
enigma,  and  that  narrow  insistence  upon  any  one  branch 
of  that  circulation  was  incompetent  to  explain  the  strik- 
ing diversities  of  ore  occurrence. 

During  the  seven  years  which  followed  1893  the  pendu- 
lum swung  steadily  away  from  the  lateral  secretion  theory 
— that  is,  the  conception  of  ore-deposits  as  being  derived 
from  the  wall-rocks  of  veins  through  the  solvent  agency 
of  laterally  moving  waters — and  the  new  ideas  which 
Posepny  had  contributed  led  to  the  overhauling  of  old 
evidence  with  a  particular  regard  to  the  distinction  be- 
tween the  circulation  of  water  in  the  vadose  zone  as  con- 
trasted with  the  deeper  horizon.  It  became  generally  ac- 
cepted that  a  large  number  of  ore-deposits,  more  especially 
those  containing  gold  and  silver  in  association  with  sul- 
phides of  the  baser  metals  within  a  matrix  of  quartz,  had 
been  laid  down  by  ascending  waters,  and  that  enrichment 
took  place,  not  from  the  wall-rock  into  the  vein  fracture, 
but  by  impregnation  from  the  fracture  outward  into  the 
encasing  rock.  During  this  period  those  of  us  who  had 
the  direction  of  mining  operations  were  given  an  oppor- 
tunity to  chew  the  cud  of  philosophic  reflection  and  to  test 
the  theories,  which  had  been  thus  far  developed,  by  ob- 
servation underground.  It  is  fair  to  say  that  then,  as 
before,  we  had  the  same  objection  to  the  wholesale  ab- 
sorption of  the  latest  scientific  dictum,  in  that  we  found 


it  too  narrow  to  cover  the  multitudinous  varieties  of  ore 
occurrence  which  were  encountered  in  our  work  from  year 
to  year. 

Then,  quite  unexpectedly,  a  new  philosopher,  of  whom 
we  mining  engineers  had  only  known  vaguely  as  a  dis- 
tinguished authority  on  the  obscure  problems  of  meta- 
Tnorphism,  came  forward  with  a  treatise  which  appealed 
to  us  from  the  very  first  on  account  of  its  striking  orig- 
inality. Professor  Van  Hise  attacked  the  subject  from 
an  entirely  novel  standpoint.*  His  essay  is  a  deductive 
reasoning  from  physical  and  chemical  principles;  it  is 
therefore  in  direct  contrast  to  the  induction  from  facts, 
which  had  hitherto  been  the  method  adopted  by  those  who 
had  investigated  the  problems  of  ore  occurrence.  For 
this  very  reason  his  work  proved  illuminating  and  sug- 
gestive along  unexpected  lines,  and  it  stimulated  the  pre- 
sentation of  a  new  array  of  facts  calculated  to  unravel 
many  perplexities.  Professor  Van  Hise  avoided  the  old 
blunder  of  sacrificing  a  broad  conception  to  a  narrow 
theory.  He  took  the  underground  circulation  of  water 
as  one  connected  manifestation  of  natural  activity,  and 
emphasized  the  fact  that  in  the  formation  of  ore-deposits 
each  of  the  branches  of  that  circulation  may,  at  different 
times  and  in  divers  places,  play  a  part.  Two  conclusions, 
however,  he  insisted  upon,  namely :  that  sulphide  ores  are 
generally  deposited  by  ascending  waters ;  and  that  second- 
ary enrichment  of  such  ore  is  effected,  to  very  consider- 
able depths,  by  the  agency  of  descending  waters. 

In  regard  to  the  latter  it  is  an  interesting  fact  that  other 
observers  had  for  several  years  ruminated  over  the  sub- 
ject of  secondary  enrichment;  and,  prompted  largely  by 
the  evidence  obtained  from  the  copper  lodes  of  the  Butte 
district,  in  Montana,  each  unknown  to  the  other,  had 
formulated  certain  views  without,  however,  making  his 
opinion  public.  The  discussion  of  the  matter  by  Profes- 
sor Van  Hise  was  accompanied  by  the  simultaneous  ap- 
pearance of  papers  on  that  subject  by  Mr.  Emmons'  and 


■"Some  Principles  Controlling  Deposition  of  Ores,"  by  C.   R.  Van  Hise, 
Trans.  A.  I.  M.  E.,  Vol.  XXX.,  pp.  27-117. 

9"The  Secondary  Enrichment  of  Ore-Deposits,"  by  S.  F.  Emmons.    Trans. 
A.  L  M.  E.,  Vol.  XXX.,  pp.  177-247. 

—  S  — 


Mr.  Weed,"  so  that  soon  we  had  an  immediate  secondary 
enrichment  of  a  most  pertinent  aspect  of  the  general  in- 
quiry. For  it  is  obvious  that  the  concentrations  of  the 
metals,  whether  due  to  ascending  waters  or  otherwise, 
are  particularly  those  which  are  of  value  to  man,  and  that 
the  investigations  which  concern  themselves  with  the  for- 
mation of  bonanzas  are  of  the  greatest  practical  value  to 
both  the  miner  and  the  economist. 

Thus,  at  last,  geology  in  relation  to  mining  reached  a 
point  where  the  most  unbelieving  utilitarian  could  not  re- 
fuse to  recognize  its  great  economic  value.  There  was  a 
time  when  the  disputation  of  the  philosophers  wearied 
the  poor  miner,  who  could  not  see  how  any  of  it  would 
guide  his  pick  amid  the  darkness  underground.  He  felt 
like  the  Scotchman  who  was  given  claret  and  found  it  sa 
thin  a  beverage  that  he  complained  that  he  could  get  "no 
forwarder"  on  it.  Subsequently  he  was  given  a  sip  of 
Chartreuse  and  exclaimed:  "Bring  me  a  mug  of  that 
stuff."  That  is  how  the  miner  felt  toward  the  last  re- 
sults of  geological  inquiry.     It  meant  business. 

It  cannot  be  doubted  that  Prof.  Van  Hise's  views  of  the 
subject,  by  inciting  opposition  no  less  than  agreement, 
stimulated  further  investigation  and  cogitation  over  the 
obscurities  of  ore-deposition;  and,  human  nature  being 
what  it  is,  opposition  was  more  productive  of  enquiry  than 
acquiescence,  for  it  was  an  active  motive  in  spurring  in- 
vestigators to  the  collection  of  fresh  data.  Within  two 
years  a  group  of  valuable  papers  gave  evidence  of  the 
studies  carried  on  by  at  least  three  most  capable  geologists, 
who  had  carried  forward  the  suggestions  already  pub- 
lished by  Prof.  Vogt,  of  Christiania,"  soon  after  Posepny 
had  presented  his  views  to  the  American  Institute  of 
Mining  Engineers,  in  the  summer  of  1893,  as  already  re- 
lated. 

A  change"  had  swept  over  the  trend  of  scientific  theory 


""The    Enrichment    of    Gold    and    Silver   Veins,"    by    Walter    H.    Weed, 
Trans.  A.  I.  M.  E.,  Vol.  XXX.,  pp.  424-448. 

"In  the  Zeitschrift  fiir  praktische  Geologic  during  1893,  1894,  1895,   1900 
and  190 1. 
"Editorial  in  the  Engineering  and  Mining  Journal  of  February  14,  1903. 


in  regard  to  the  origin  of  ores.  Not  long  before,  students 
of  the  subject  had  been  transported  with  the  idea  of  water 
action,  now  they  were  asked  to  diflferentiate  in  magmas. 
Time  had  restored  the  balance.  Ten  years  ago  Prof. 
Posepny  started  a  discussion  which  emphasized  the  im- 
portance of  aqueous  agencies  in  the  distribution  of  ores; 
tliis  was  followed  by  an  era  of  investigation  into  under- 
ground waterways,  the  effects  induced  by  surface  drainage 
and  the  maintenance  of  subterranean  circulation  by  gravi- 
tative  stress;  this  development  of  the  science  was  fitly 
accentuated  by  the  philosophic  deductions  of  Prof.  Van 
Hise,  supplemented  by  the  practical  inference  made  on  the 
subject  of  secondary  enrichments  by  Messrs.  Emmons, 
Weed  and  others. 

During  this  period  there  were  several  investigators  who 
chafed  under  the  undue  prominence  given  to  aqueous 
agencies  and  demurred  to  the  obvious  neglect  of  a  funda- 
mental factor  in  the  genesis  of  ore-deposits — a  factor  long 
recognized  by  the  miner  in  his  proverbial  fondness  for 
"porphyry"  as  a  favorable  association  for  rich  mines. 
While  our  American  authorities  were  waxing  enthusiastic 
over  the  work  of  Posepny,  Prof.  Vogt  was  making  a  care- 
ful inquiry  into  the  differentiation  of  rock  magmas  and  had 
come  to  the  conclusion  that  the  normal  terrestrial  water 
circulation  played  a  minor  part  in  the  primary  origin  of 
certain  deposits,  however  much  it  may  have  affected  their 
later  concentration,  from  such  portions  of  the  magma  as 
were  rich  in  metals,  along  the  contact  with  sedimentary 
rocks.  When  Prof.  Van  Hise  elucidated  the  principles 
controlling  the  underground  circulation  of  waters  near  the 
earth's  exterior  as  the  determining  factor  in  the  great 
process  of  ore  formation.  Prof.  Kemp"  pointed  out 
that  the  greater  number  of  deposits  of  gold,  silver 
and  copper  ores,  as  known  to-day,  are  near  igneous 
rocks  with  which  he  believed  them  to  be  genetically  con- 
nected. A  discussion  arose  between  Professors  Van  Hise 
and  Kemp  which  served  a  most  useful  purpose  and  was 
followed  with  keen  interest  by  the  mining  fraternity. 


""The  Role  of  the  Igneous  Rocks  in  the  Formation  of  Veins,"  by  J.  F. 
Kemp.     Trans.  A.  I.  M.  E.,  Vol.  XXXI.,  pp.  169-198. 


Before  this  interesting  controversy  occurred,  Mr.  J.  E. 
Spurr,  in  his  examination  of  the  Yukon  District,  in 
Alaska,"  had  become  impressed  with  the  evidence  of  ore- 
segregation  afforded  by  a  series  of  closely  related  rocks  in 
the  Forty-Mile  region,  and  in  his  report,  published  three 
years  ago,  he  announced  a  radical  departure  from  accepted 
views  by  describing  the  gold-quartz  veins  of  the  Yukon 
as  the  end-product  of  rock-segregation.  This  he  ex- 
plained as  the  result  of  a  progressive  increase  in  silicifica- 
tion,  by  means  of  which  a  basic  hornblendic  granite  passes 
into  a  quartz  feldspar  rock,  termed  "alaskite" ;  the  changes 
continuing  until  the  alaskite  resembles  a  quartzite  and  is 
only  distinguishable  from  a  typical  quartz-vein  by  small 
porphyritic  crystals  of  feldspar.  Mr.  Spurr  holds  that 
certain  gold-bearing  quartz-veins  in  the  Yukon  have  orig- 
inated by  a  process  of  magmatic  segregation,  and  that  they 
represent  merely  the  siliceous  extreme  of  the  process,  the 
final  stage  of  which  is  marked  bv  a  magma  so  attenuated 
as  to  be  described  as  highly  heated  water  heavily  charged 
with  silica  and  other  mineral  matter,  including  gold. 

These  theories  have  been  a  stimulant  to  widespread  ob- 
servation. In  the  earlier  part  of  last  year  Prof.  Joseph 
Barrell  published"  the  result  of  his  researches  into  the 
physical  effects  of  contact  metamorphism,  affording  there- 
by  certain  data  concerning  the  liberation  of  enormous  vol- 
umes of  gas  due  to  the  effects  of  igneous  masses  upon  the 
sedimentary  rocks  which  they  penetrate.  He  gave  also 
information  concerning  the  mineralogic  changes  induced 
by  metamorphism,  affording  valuable  hints  which  other 
geologists  have  not  been  slow  to  utilize.  Mr.  W.  H. 
Weed,  the  indefatigable  observer  that  he  is,  has  applied 
the  views  of  Vogt  and  Kemp  to  particular  occurrences  of 
ore  which  he  has  examined,  with  the  result,  among  others, 
that  he  has  elucidated"  the  particular  conditions  which 
render  the  contacts  of  igneous  and  sedimentary  rocks  such 
a  favorable  locus  for  ore  occurrence.     This  he  has  found 


""Geology  of  the  Yukon  Gold  Belt,"  by  J.  E.  Spurr.  i8th  Annual  Re- 
port, U.  S.  Geological  Survey,  Part  iii.,  p.  297,  1898. 

""The  Physical  Effects  of  Contact  Metamorphism,"  by  Joseph  Barrell. 
Am.  Jour.  Sci.,  Vol.  XIII.,  April,  1902,  p.  279. 

"Ore-Deposits  Near  Igneous  Contacts,"  by  Walter  Harvey  Weed.  Trans. 
A.  I.  M.  £.,  Vol.  XXXII.,  read  at  New  Haven,  October,  1902. 


to  arise  from  the  fact  that  the  sedimentary  strata  arc  made 
porous  by  thermal  metamorphisrn,  which  may  be  com- 
pared to  the  results  produced  by  burning  a  clay  into  a 
brick.  Finally,  Prof.  Kemp"  has  followed  up  his  argu- 
m.ent  for  the  derivation  of  ores  directly  from  a  magma, 
and  has  pointed  to  the  activity  which  vulcanism  is  apt  to 
give  to  thermal  circulation.  His  discussion  of  the  dis- 
tribution of  the  ground-water  in  mining  regions  draws 
attention  to  the  confused  ideas  which  exist  concerning 
water  distribution  underground,  a  confusion  due,  I  be- 
lieve, to  the  fact  that  the  ground-water  level  is  artificially 
depressed  by  shafts  and  other  mine  workings. 

In  shaping  the  ideas  of  those  engaged  in  the  study  of 
ore-deposits,  one  paper,  as  yet  not  mentioned,  demands 
proper  reference.  I  refer  to  Mr.  Lindgren's  essay  on  con- 
tact deposits"  which  appeared  in  1901.  This  paper  car- 
ries forward  Vogt's  views,  previously  expressed,  as  ap- 
plied by  ]\Ir.  Lindgren  to  occurrences  of  ore  in  the  United 
States.  It  is  a  contribution  which,  while  modest  in  its 
claims,  has  no  doubt  influenced  to  a  notable  degree  the 
ideas  of  others,  such  as  Mr.  Weed,  who  have  brought  for- 
ward more  comprehensive  theories;  and  as  a  thoroughly 
scientific  enquiry  into  an  obscure  matter,  it  forms  one  of 
the  very  best  contributions  to  the  discussion  of  ore-de- 
posits. By  throwing  the  weight  of  his  researches  against 
the  water  extremists,  Mr.  Lindgren  gave  strong  support 
to  the  advocates  of  magmatic  differentiation  in  its  bearing 
upon  the  origin  of  ores ;  the  influence  of  his  work  is  plainly 
discernible  in  the  discussion  to  which  we  now  come. 

This  discussion  took  place  at  the  regular  monthly  meet- 
ings of  the  Geological  Society  of  Washington,  a  society 
composed  largely  of  the  members  of  the  United  States 
Geological  Survey.  At  the  meeting  of  January  14,  1903, 
Mr.  Weed  brought  forward  a  genetic  classification.  It 
was  discussed  by  Messrs.  Emmons,  Spurr  and  Lindgren. 


""Igneous  Rocks  and  Circulating  Waters  as  Factors  in  Ore-Deposition," 
by  J.  F.  Kemp.  Trans.  A.  1.  M.  E.,  XXXII.,  read  at  New  Haven,  October, 
1902. 

^'"The  Character  and  Genesis  of  Certain  Contact  Deposits,"  by  Walde- 
mar  Lindgren.     Trans.  A.  L  M.  E.,  Vol.  XXXL,  pp.  226-244. 


Mr.  Spurr  offered  an  alternative  classification.  At  the 
next  meeting,  held  on  February  25,  the  discussion  was  re- 
sumed with  much  interest  in  the  presence  of  a  strikingly 
representative  gathering  of  geologists.  Professors  Van 
Hise  and  Kemp,  who  are  non-resident  members,  were 
especially  asked  to  be  present,  and  the  writer,  who  is  not  a 
member,  was  also  most  courteously  invited  to  come  and 
take  part  in  the  debate.  It  proved  to  be  full  of  spirit.  Mr. 
Emmons  led  off  with  a  suggestive  introduction,  then  Prof. 
Kemp  spoke  up  for  the  role  of  the  igneous  rocks  as  against 
a  too  positive  insistence  upon  the  adequacy  of  meteoric 
waters ;  after  him  Mr.  Ransome  and  the  writer  followed, 
taking  a  line  of  argument  which  went  between  the  extreme 
views  upon  the  subject.  When  Prof.  Van  Hise,  as  the 
exponent  of  the  agency  of  meteoric  waters,  began  an  at- 
tack upon  those  who  pushed  the  igneous  theory  too  far, 
there  was  the  keenest  interest  in  his  remarks.  In  his  re- 
peated request  for  criteria  justifying  the  more  recent  views 
on  magmatic  differentiation,  he  was  unusually  earnest  in 
his  manner,  insisting  that  his  critics  were  too  hasty  in  the 
promulgation  of  new  theories.  This  prompted  a  sharp 
reply  from  Mr.  Weed,  and  the  personal  element  in  the  con- 
troversy threatened  to  dominate  the  discussion.  How- 
ever, Prof.  Kemp,  Mr.  Lindgren  and  others  offered  a  few 
friendly  remarks  and  the  debate  was  finally  wound  up 
with  the  feeling  that  it  had  proved  most  stimulating  and 
suggestive. 

In  this  debate  it  was  seriously  questioned  whether  the 
younger  men  were  justified  in  publishing  comprehensive 
theories  on  the  evidence  at  present  available.  It  was  held 
by  some  that  the  premature  statement  of  explanations,  as 
yet  not  confirmed  by  sufficient  data,  would  prove  an  ob- 
stacle to  reliable  testimony,  by  prejudicing  the  ideas  of  in- 
vestigators in  the  field.  One  or  two  of  the  veteran  geolo- 
gists plainly  deprecated  anything  approaching  hastiness  in 
the  framing  of  generalizations  from  few  facts,  while  cer- 
tain active  workers  among  the  supporters  of  igneous  views 
in  ore-deposition  were  inclined  to  deny  the  claim  of  the 
advocates  of  meteoric  waters  to  the  possession  of  a  demon- 
strated theory  which  could  only  be  set  aside  by  newer 


—  13  — 


views  based  upon  ample  evidence.  This  is  an  interesting 
situation,  such  as  has  arisen  before  in  the  development  of 
science." 

"Without  speculation  there  is  no  good  and  original  ob- 
servation/' This  was  said  by  the  author  of  'The  Origin 
of  Species,"  himself  a  man  who,  as  his  friend  Huxley 
said,  "abhorred  mere  speculation  as  nature  abhors  a 
vacuum."  These  are  statements  which  must  be  taken 
with  an  appreciation  of  the  men  who  made  them.  Darwin 
held  that  true  explanations  of  natural  operations  could 
only  come  from  the  painstaking  sifting  of  a  vast  amount 
of  evidence,  some  of  which  might  be  ill-assorted  and  even 
contradictory.  He  himself  worked  indefatigably  for  four- 
teen years  on  the  species  question  before  he  even  pub- 
lished an  outline  of  his  views,  and  he  spent  practically  all 
the  working  hours  of  a  long  life  in  explaining,  confirming 
and  correcting  his  thesis.  He,  at  first,  had  to  face  the 
charge  of  promulgating  a  theory  based  on  insufficient  data, 
but  lived  long  enough  to  drive  it  home  to  the  leading  intel- 
lects of  his  generation.  A  theory  is  like  a  revolution,  if 
it  is  made  good  it  receives  honor,  if  it  fails  to  hold  its  own 
it  becomes  regarded  as  a  mere  unwarrantable  disturbance. 

Of  late  those  of  us  who  are  interested  in  mining  and  in 
the  technical  knowledge  which  aids  that  industry  have 
been  stimulated  from  time  to  time  by  the  projection  across 
the  intellectual  horizon  of  a  succession  of  theories  ex- 
planatory of  the  origin  of  metallic  ores.  One  theory  has 
hardly  been  put  to  the  trial  of  observation  before  another 
has  collided  with  it,  so  that  to-day  a  striking  diversity 
of  views  claims  our  attention,  and  we  are  excited  to  a 
high  degree  of  interest  in  the  study  of  ore-deposits.  Vet- 
eran authorities  are  inclined  to  deprecate  the  unseemly 
haste  which  appears  to  them  to  mark  the  publication  of 
new  ideas,  and,  pointing  to  the  philosophic  patience  of  the 
Lyells  and  Darwins  of  an  older  generation,  who  collected 
data  for  half  a  lifetime  and  ruminated  over  them  for  most 
of  the  other  half  before  they  came  forward  with  well 
digested  and  splendidly  supported  explanations  of  natural 


^^The   remarks  which   follow  formed  an  editorial  in  the  Engineering  and 
Mining  Journal  of  March  7,  1903. 

—  14  — 


phenomena,  they  feel  justified  in  objecting  to  the  confu- 
sion created  by  the  simultaneous  submission  of  numerous 
speculations  of  a  revolutionary  character. 

We  confess  to  a  feeling  of  sympathy  with  both,  and  a 
keen  appreciation  of  the  aggressiveness  of  the  younger 
men.  "The  scientific  man  accepts  his  limitations  and  does 
not  expect  to  arrive  at  absolute  verity.  He  observes,  and 
when  he  has  advanced  far  enough  to  begin  to  generalize, 
he  formulates  his  ideas  as  an  hypothesis  to  serve  as  a 
basis  on  which  to  work  until  "some  one  has  suggested 
something  better."  This  was  said  by  Huxley.  He  had 
been  too  long  obstructed  by  the  Mosaic  cosmogony  not  to 
feel  a  bitter  dislike  of  any  artificial  hindrance  to  scientific 
investigation ;  in  his  opinion  a  theory  was  to  be  respected 
so  long  as  it  served  its  purpose  of  directing  observation 
along  the  right  road,  but  as  soon  as  it  played  the  part  of  a 
barricade  it  behooved  all  seekers  after  knowledge  to  tear  it 
down  and  proceed  unhindered  along  the  narrow  way 
which  leads  to  truth.  This  is  not  an  unruly  spirit,  but 
sound  common  sense ;  it  may  indeed  have  fathered  a  few 
bastards  like  the  Bathybius  theory  ef  Huxley  himself  or 
the  "Polarity"  of  Edward  Forbes,  but  it  has  bred  a  prog- 
eny of  splendid  philosophies,  from  the  Nebular  Hypothe- 
sis to  Evolution. 

Under  the  present  dispensation  of  scientific  research 
there  are  ten  times  as  many  investigators  along  any  line 
of  inquiry  as  there  were  fifty  years  ago.  Conjecture, 
speculation  and  theory  are  enormously  more  active  than 
they  were  in  the  days  when  geology  lay  in  the  cradle  of 
Lyell's  'Principles.'  It  is  useless  to  try  to  smother  the 
eager  voices  which  earnestly  hasten  to  speak  of  that  which 
they  have  seen.  Let  them  speak  out,  and  then  correct 
them  if  they  are  wrong,  disprove  them  if  they  are  too 
hasty,  so  that  out  of  the  correction  as  out  of  the  sugges- 
tion some  truth  shall  come. 

The  fact  is,  that  in  dealmg  with  such  a  tremendous 
subject  as  ore-deposition  there  will  always  be  much  con- 
cerning which  we  can  never  be  certain.  Inductive  rea- 
soning from  facts  will  carry  us  down  to  the  bottom  of 
the  mine,  but  deduction  from  principles  must  then  carry 

—  IS  — 


the  fairy  wand  of  the  scientific  imagination,  which  finds  a 
way  into  the  depths  where  human  eye  will  never  be  able 
to  penetrate.  Therefore,  positiveness  of  statement  is  im- 
possible, and  a  reasonable  probability  is  the  utmost  goal 
of  our  unwearied  seeking. 

Ill-considered  speculations  are  obviously  undesirable, 
but  it  seems  to  us  that  the  greater  harm  may  be  done 
by  the  failure  to  discuss  the  unverified  hypotheses  of  the 
day.  If  a  man  is  a  fool,  let  him  alone  in  his  folly ;  but  if  a 
geologist,  quickened  by  the  acquirement  of  new  evidence, 
hastens  to  formulate  a  conjecture,  thank  him  for  what  is 
good  in  it  and  combat  him  for  what  is  wrong.  An  erro- 
neous hypothesis  has  before  now  led  the  way  to  the 
ascertainment  of  the  truth.  It  is  better  than  nothing  to 
the  seeker  after  order  amid  the  maze  of  phenomena. 
Progress  depends  upon  criticism  of  hypotheses,  upon  the 
sifting  of  facts,  the  elimination  of  fallacy  until  there  only 
remains  that  residuum  which  is  proved  to  be  true.  There 
is  too  little  discussion  on  ore-deposits,  and  too  much  of 
essay  writing.  It  is  possible  to  criticise  with  penetration 
and  yet  to  be  polite.  Such  criticism  is  a  compliment  to 
the  author  and  a  gain  to  all  who  are  interested  in  the 
subject.  We  advocate  a  free  discussion  of  principles,  a 
winnowing  of  fact  from  fancy,  so  that  the  solid  observa- 
tion may  be  separated  from  the  light  chaff  of  careless 
guess.  To  the  miner,  to  whom  the  subject  of  ore-depo- 
sition is  vitally  important,  it  is  of  paramount  interest 
that  the  authorities  on  the  subject  should  come  into  the 
arena  and  discuss  the  principles  at  issue,  to  the  greater 
glory  of  geology  and  the  general  enlightenment  of  the 
community. 

It  is  for  this  reason  that  the  discussion  was  published 
in  the  Engineering  and  Mining  Journal,  and  it  is  for  the 
same  reason  that  the  discussion  is  now  reprinted  with 
additions,  in  pamphlet  form.  There  has  been  added  a 
supplementary  paper"  by  Mr.  C.  W.  Purington,  who 
submits  considerations  prompted  by  the  foregoing  discus- 

•Which   appeared    in    the   Engineering  and   Mining  Journal  of  June   6th, 
rjth  and  20th,  1903. 

—  16  — 


sion  and  based  upon  his  own  observations  in  remote  min- 
ing regions.  Such  observations  are  of  the  greatest  value, 
for  they  afford  the  material  needed  to  balance  the  ten- 
dency toward  generalization,  to  which  all  of  us  are  only  too 
prone.  The  mining  engineers  who,  as  a  rule,  are  shy  of 
participation  in  open  debate,  possess  opportunities,  by  the 
recording  of  observations  made  from  day  to  day  in  the 
underground  workings  of  mines,  fc/  collecting  the  facts 
upon  which  the  theories  of  the  geologist  will  be  founded. 
At  all  events,  they  contribute  the  rough  stones  which  the 
specialist  will  place  in  their  proper  position,  adding  thereto 
a  cementing  knowledge  which  shall  bind  together  the 
sifted  data  into  a  firm  and  substantial  material,  fit  eventu- 
ally for  the  construction  of  that  comprehensive  theory 
which  the  miner  and  the  geologist  alike  are  seeking. 

T.  A.  RiCKARD, 

Editor  of  The  Engineering  and  Mining  Journal. 


xy  — 


THE    GENETIC    CkASSIFICATION 
OF    ORE-DEPOSITS 

A  PROPOSAL  AND  A  DISCUSSION. 

A  tentative  genetic  classification  of  ore-deposits  having- 
been  proposed  by  Mr.  W.  H.  Weed,  and  submitted  by 
him  to  those  who  would  be  likely  to  take  a  particular 
interest  in  the  subject,  a  meeting  of  the  Geological  Society 
of  Washington  was  held  on  January  14,  1903,  with  a  view 
to  eliciting  a  discussion  upon  the  matter. 
S.  F.  EMMONS.  The  debate  was  opened  by  Air.  Emmons,  who  re- 
called the  conditions  confronting  Clarence  King,  when, 
in  1879,  it  fell  to  him  to  shape  the  policy  that 
should  direct  the  economic  work  of  the  Geological 
Survey.  At  that  time  but  little  progress  had  been  made 
toward  a  clear  understanding  of  the  general  principles  of 
ore-genesis.  King  believed  that  systematic  study  of  the 
important  mining  districts  of  the  country  would  discover 
such  general  principles  and  would  result  in  material  con- 
tributions to  the  then  somewhat  neglected  study  of  ore- 
deposition. 

Mr.  Emmons  continued :  Investigations  carried  out  by 
the  Survey  during  the  past  twenty  years  have  justified 
King's  belief  in  the  policy  then  initiated.  The  careful 
study  of  many  mining  districts  in  this  country  has  not 
only  added  directly  to  our  knowledge  of  ore-deposits,  but 
it  has  supplied  a  mass  of  selectively  recorded  observa- 
tions that  have  made  possible  the  recognition  of  such  gen- 
eral principles  as  those  enunciated  by  both  Mr.  Weed 
and  myself  in  regard  to  secondary  sulphide  enrichment, 
by  Mr.  Lindgren  with  reference  to  metasomatic  processes 
and  contact  metamorphism,  and  by  Prof.  Van  Hise  in 
connection  with  the  circulation  and  action  of  meteoric 
waters.  While  a  great  deal  remains  to  be  done  before 
the  processes  connected  with  ore-deposition  are  fully  un- 
derstood, there  has  undoubtedly  been  a  great  advance  in 

—18— 


this  direction  during  recent  years,  and  we  are  perhaps      S.  F.  EMMOVS:,/ 
now  in  a  position  to  discuss  a  preliminary  classification 
of  ore-bodies  on  the  basis  of  genesis. 

I  desire  to  define  my  own  position,  since  my  views,  as 
expressed  in  the  first  report  on  Leadville,  have  been  mis- 
understood. In  that  report,  being  yet  new  to  the  study, 
I  declined  to  discuss  the  ultimate  source  of  the  metallic 
minerals,  but  as  regards  the  immediate  source — ^that  is, 
how  they  at  last  reached  their  present  position — I  said 
that  the  waters  which  deposited  them  were  descending 
from  the  porphyry  contact  into  the  body  of  the  underly- 
ing limestone,  and  did  not  come  up  through  fissures  in  the 
Archean,  as  was  then  maintained  by  some  mining  engi- 
neers, who  based  their  statements  not  on  observation  but  '  . ' 
on  theory.  I  also  stated  my  belief  that  the  ores  had  been  > 
leached  from  the  neighboring  porphyry  bodies.  My  state- 
ments with  regard  to  these  particular  deposits  have  been 
construed  to  class  me  among  the  school  of  descensionists, 
and  this  construction  still  seems  to  hold  among  some 
writers.  In  point  of  fact,  as  shown  in  later  writings, 
while  recognizing  that  most  deposits  were  formed  di- 
rectly by  ascending  waters,  I  differ  from  the  ascension- 
ists,  especially  as  voiced  by  Posepny,  mainly  in  believing 
that  as  regards  their  ultimate  source  the  metallic  minerals 
were  brought  from  great  depths  to  the  vicinity  of  the 
surface  or  within  reach  of  meteoric  waters,  rather  in  the 
magma  of  igneous  rocks  than  in  aqueous  solution. 
Hence,  in  1893,  I  welcomed  Vogt's  recent  demonstration 
that  certain  iron  ore-deposits  had  been  formed  by  a  mag- 
matic  differentiation  during  the  cooling  of  ?gneous  rocks, 
as  a  line  of  investigation  that  would  prove  fruitful  in 
determining  the  probable  ultimate  origin  of  the  material 
of  our  deposits;  but  I  still  believe,  as  I  stated  then,  that 
most  of  our  deposits  in  their  present  form  are  the  result 
of  a  later  concentration  by  circulating  waters  of  meteoric 
origin.  A  pneumatolytic  origin  for  a  certain  class  of  de- 
posits, especially  near  the  contacts  of  igneous  rock  with 
limestone,  can  be  demonstrated  by  their  mineral  associa- 
tion, and  it  is  very  possible  that  some  of  the  metallic  con- 
tents of  other  deposits,  where  this  mineral  association  is 


S.  F.  EMMONS,  wanting,  may  have  originally  been  separated  from  an 
igneous  magma  by  pneumatolysis.  If,  however,  in  the 
present  condition  of  the  deposit,  the  agency  of  circulating 
waters  is  the  only  one  that  can  be  actually  demonstrated, 
and  was  the  final  cause,  it  seems  to  me  that  this  origin 
should  be  the  one  to  be  recognized  in  the  classification. 

W.  H.  WEED.  In  his  prefatory  remarks,  Mr.  Weed  emphasized 
the  divergent  views  of  those  who  maintained  that 
most  ore-deposits  were  the  work  of  underground  me- 
teoric waters,  which  had  derived  their  mineral  contents 
from  the  rocks  traversed,  and  those  who  held  that  the 
greater  number  of  workable  ore-bodies  resulted  from  the 
gases  and  vapors  given  off  from  fused  magma  in  the 
process  of  cooling.  He  firmly  believed  that  igneous  in- 
trusions had  furnished  not  only  the  heat  for  most  hot 
waters,  but  also  the  mineral  contents,  either  directly  as 
differentiations  or  emanations,  or  through  the  leaching  of 
the  rocks  by  vapors  and  heated  waters. 

Mr.  Weed  remarked  that  probably  everyone  who  had 
written  or  lectured  upon  ore  deposits  has  felt  the  need  of 
a  systematic  arrangement  of  his  data,  and  has  adopted 
some  sort  of  classification.  Such  grouping  was  important 
because  it  facilitated  discussion  of  the  differences  between 
ore-deposits,  and  lent  itself  to  the  orderly  presentation 
of  facts  and  descriptions.  The  provisional  classification 
which  he  submitted  was  an  attempt  of  this  kind.  He 
owed  much  to  the  work  of  others,  particularly  of  Vog^, 
Eeck  and  Kemp,  but  he  had  aimed  to  give  precedence  to 
genetic  distinctions,  followed  by  those  based  on  structure 
and  on  mineralog\'. 

Genetic  Classification  of  Ore-Deposits. 

I.  Igneous   (magmatic  segregations.) 
A.  Siliceous. 

a.  Masses — Aplitic  masses,  Ehrenberg,  Shar- 

tash. 

b.  Dikes — Beresite  or  aplite,  Berezovsk. 

c.  Quartz   veins,   Alaska,   Randsburg,   Black 
'^Hills. 


B.  Basic.  W.  H.  WEED. 

a.  Peripheral  masses. 

Copper. 

Iron. 

Nickel. 

b.  Dikes. — Titaniferous     iron,     Adirondacks, 

Wyoming. 

II.  Igneous    Emanations.     Deposits    formed   by    gases 
above  or  near  the  critical  point,  e.  g.,  365''  C. 
and  200  atmospheres  for  Hp. 

A.  Contact  Metamorphic  Deposits. 

Characterized  by  gangue  consisting  essen- 
tially of  garnet,  epidote,  actinolite,  cal- 
cite  and  other  lime-alumina  silicates. 

a.  Deposits  confined  to  contact: 

1.  Magnetite  deposits. 

2.  Chalcopyrite  deposits,  Kristiania  type. 

3.  Gold  ores,  Bannock  type. 

b.  Deposits  impregnating  and  replacing  beds 

of  contact  zone: 

1.  Chalcopyrite  deposits — (a)   pyrrhotite 

ores,    (b)   magnetite    ores,  Cananea 
type. 

2.  Gold  tellurium  ores,  Elkhorn  type. 

3.  Arsenopyrite  ores,  Similkameen  type. 

B.  Veins  (closely  allied  to  magmatic  veins  and  to 

division  IV.). 

a.  Cass  iter  ite — Cornwall. 

b.  Tourmaline  copper — Sonora. 

c.  Tourmaline  gold — Helena,   Mont.;   Minas 

Geraes,  etc. 

d.  Augite  copper,  etc. — ^Tuscany. 

III.  Fumarolic  Deposits.     MetalHc  oxides,  etc.,  in  clefts 

in  lavas.     No  commercial  importance. 
Copper. 
Iron,  etc. 

IV.  Gas — Aqueous   (pneumato-hydato-genetic)   deposits. 

Igneous  emanations,  or  primitive  water  mingled 
with  ground-waters. 


W.  H.  WEED.  A.  Filling  Deposits. 

a.  Fissure  veins. 

b.  Impregnation  of  porous  rocks. 

r.  Cementation  deposits  of  breccias. 
B.  Replacement  Deposits. 

a.  Propylitic — Comstock. 

b.  Sericitic  kaolinic. 

Calcitic. 

Copper  silver.  ^ 

Silver  lead — Qausthal. 

c.  Silicic  dolomitic — silver  lead — Aspen. 

d.  Silicic  calcitic — Cinnabar. 

e.  Sideritlc   silver  lead — Coeur  d'Alene,   Slo- 

can,  Wood  River. 

f.  Biotitic  gold  copper — Rossland. 

g.  Fluoric  gold  tellurium — Cripple  Creek. 
h.  Zeolitic. 

Structural  types  of  above: 

a.  Fissure  veins. 

b.  Volcanic  shocks — Nag}^ag,  Cripple  Creek. 

c.  Contact  chimneys — Judith. 

d.  Dike  replacements  and  impregnations. 

e.  Bedding     or     contact     planes — Leadville, 

Mercur. 
/.  Axes  of  folds. 

Synclinal  basins. 

Anticlinal  saddles — Bendigo,  Elkhom. 
V.  Meteoric  Waters.     (Surface  derived.) 

A.  Underground. 

a.  Veins. 

b.  Replacements. 

Iron   ores — Michigan. 
Copper  ores — Michigan, 
Lead. 
Zinc. 

c.  Residual. 

Gossan  iron  ores. 
Manganese   deposits. 

B.  Surficial. 

a.  Chemical. 

Bog  iron  ores. 


Copper  ores.  W.  H.  WEED. 

Sinters. 
b.  Mechanical. 
Gold  placers. 
Tin  placers.  _ 

Sedimentary  beds,  iron  ore,  etc. 
VI.  Metamorphic   Deposits.     Ores     concentrated   from 
older    rocks    by    dynamo — and  regional — ^meta- 
morphism. 

In  explanation  of  the  foregoing  scheme  of  classifica- 
tion, Mr.  Weed  said:  'The  six  primary  subdivisions,  as 
given  by  me,  might  be  reduced  to  two:  First,  those  of 
direct  or  indirect  igneous  origin,  and,  second,  those  due 
to  aqueous  agencies.  As,  however,  there  are  intermedi- 
ate types,  I  have  deemed  it  best  to  make  the  subdivisions 
given.  These  six  primary  subdivisions  have  been  ar- 
ranged to  show  gradation,  from  the  magmatic  segrega- 
tion of  original  igneous  rocks,  through  the  deposits  di- 
rectly or  indirectly  due  to  the  emanations  from  igneous 
rocks,  and  up  to  those  due  entirely  to  aqueous  agencies. 

This  classification  practically  ignores  form  as  being 
a  factor  of  economic  but  not  of  genetic  importance.  This 
point  needs  emphasis,  since  even  the  more  recent  writers 
on  ore-deposits  have  grouped  them  into  veins  and  irregu- 
lar deposits.  From  a  genetic  standpoint,  it  is  a  minor 
detail  whether  ores  are  deposited  in  tabular  form  (veins)  ^ 
or  irregular  masses,  such  as  characterize  contact  de- 
posits. It  is  admitted  that  genetic  considerations  affect 
the  shape  and  form  of  ore-bodies ;  but  it  Is  apparent  that 
if,  for  example,  hot  mineralized  waters,  ascending  a  fis- 
sure through  flat  sedimentary  rocks,  may  fill  part  of  the 
fissure  forming  a  vein,  they  may  at  the  same  time  replace 
limestone  when  these  rocks  form  the  fissure  wall,  and 
thus  form  so-called  chamber  deposits.  Examples  of  this 
are  not  uncommon. 

Thus  it  follows  that  a  hard  and  fast  line  cannot  be 
drawn  for  replacement  deposits — a  most  important  type 
and  a  distinction  of  vital  importance  to  the  miner.  But 
my  own  experience  confirms  the  observations  of  Mr. 
Emmons  and  others,  that  the  veins  formed  by  'fissure 
filling'  are  accompanied  by  alteration  and  frequently  by 

—  23  — 


W.  H.  WEED,  replacement  of  the  wall-rock,  and  hence  belong  to  both 
classes. 

A  careful  study  of  the  peculiar  Black  Hills  gold  de- 
posits by  Irving  shows  that  the  Vertical/  a  mere  fissure 
traversing  various  rock  formations,  has  been  the  feeder 
or  conduit  for  mineral  solutions — replacing  congenial 
beds.  Another  familiar  example  is  seen  in  the  Rico, 
Colorado,  deposits,  as  given  by  Mr.  Rickard  n.  his  de- 
scription of  the  Enterprise  mine.  At  Cripple  Creek  the 
well  marked  vein  is  often  an  insignificant  quartz  thread, 
or  even  a  fissure,  though  the  rock  for  several  feet  on  each 
side  is  altered,  as  described  by  Rickard,  and  carries  high 
value  in  gold.  Such  fissures  might  readily  be  overlooked 
in  mining,  or,  if  discovered,  adduced  as  proof  of  post- 
mineral  fissuring  of  the  deposit.*  Such  structural  fea- 
tures are  of  the  highest  importance  in  the  economic  work- 
ing of  mines — a  fact  recognized,  perhaps,  but  never  fully 
appreciated  until  the  presentation  of  Emmons'  masterly 
treatise  on  the  ''Structural  Features  of  Ore-Deposits,"  one 
of  the  earliest  of  the  many  contributions  to  the  geology  of 
ore-deposits,  which  have  placed  the  mining  fraternity 
under  deep  obligation  to  this  author. 

It  should  be  understood  that  no  argument  will  be 
attempted  to  prove  the  particular  origin  of  any  particular 
deposit,  as  such  evidence  would  be  out  of  place  in  the 
present  paper.  The  localities  mentioned  are  such  as  ap- 
pear from  a  critical  examination  of  the  evidence  by  vari- 
ous trustworthy  observers  to  illustrate  the  proposed 
classes.  Whether  they  are  of  such  character  or  not,  is  a 
subject  for  entirely  separate  inquiry  and  discussion.  It  is 
assumed  also  that  the  reader  is  familiar  with  the  work  of 
the  well  known  writers  on  the  genesis  of  ore-deposits, 
since  it  would  be  out  of  place  to  repeat  the  evidence  pre- 
sented by  these  authors,  and  readily  accessible.  It  will 
be  observed  that  the  classification  recognizes  and  enlarges 
upon  the  magmatic  segregation  and  eruptive  after-action 
groups  of  Vogt. 

The  first  class  embraces  only  deposits  which  are  due  to 
the  differentiation  of  igneous  rocks.     These  types  of  ore 

*See  Posepny's  criticism  of  this;  St.  Avoid.  Trans.  A.  I.  M.  E.,  VoL 
XXIII.,  p.  312- 


deposits  are  but  little  known  in  this  country  and  have  been  W.  H.  WEED. 
best  studied  by  the  Norwegian  geologist,  Vogt.  Under  the 
general  term  of  magmatic  segregations,  I  have  distin- 
guished masses  from  dikes.  The  first  term  embraces  the 
irregular  contact  deposits  of  iron  ores,  copper  ores  and 
nickel  ores,  commonly  associated  with  basic  rocks,  and 
due  to  extreme  differentiation  of  these  rocks.  Besides 
masses,  I  have  added  the  dikes  which  represent  extreme 
differentiation  products  of  the  magmas  under  different 
physical  conditions,  the  basic  differentiations  being 
titaniferous  iron  ores,  the  examples  of  which  are  those 
of  the  Adirondacks  and  of  Ontario,  described  by  Prof. 
Kemp  and  by  Prof.  Adams,  while  recently  Mr.  Lindgren 
has  described  an  example  in  Wyoming.  Quartz  veins, 
while  not  so  generally  admitted  to  be  an  extreme  acid 
product  of  the  differentiation  of  igneous  rocks,  are,  I  con- 
sider, now  admitted  by  many  geologists  to  grade  into 
pegmatites  and  those  aplitic  rocks  grouped  under  the 
name  of  alaskites,  concerning  the  derivation  of  which 
there  is  no  dispute.  Van  Hise  records  examples  in  the 
Black  Hills  which  seem  to  show  an  orderly  transition  from 
pegmatite  veins  to  normal  quartz  veins.  The  quartz  veins 
occur  farther  away  from  the  igneous  core  than  the 
pegmatite. 

The  group  is  based  upon  so  extensive  a  mass  of  evi- 
dence that  it  needs  but  little  in  the  way  of  comment,  save 
in  explanation  of  the  subdivisions  adopted  and  the  reasons 
therefor. 

Ore-Deposits  Formed  by  Igneous  Emanations. — The 
second  subdivision  is  somewhat  different  from  anything 
heretofore  proposed,  and  it  is  limited  to  deposits  produced 
by  the  gases  given  off  by  highly  heated  igneous  magmas. 
I  may  add  that  the  term  'pneumatolytic,'  which  is  used  as 
synonymous  with  the  term  'gas'  in  the  classification  under 
discussion,  implies  the  action  of  heated  gases  and  vapors 
upon  solids.  The  evidence  that  ore-deposits  are  formed 
under  such  conditions,  and  not  by  ordinary  waters  or  by 
steam  and  other  gases  at  lower  temperatures,  is  afforded 
by  the  mineral  composition  of  the  ores,  and  especially 
when  examined  in  thin  section  under  the  microscope. 

—  25  — 


W.  H.  WEED.  Contact  Metaniorphic  Deposits. — ^Deposits  of  this  class 

occur  at  or  near  the  contacts  of  intrusive  granitic  or  por- 
phyritic  rocks.  The  characteristic  minerals  associated 
with  the  ores  are  garnet,  epidote,  vesuvianite,  specular 
hematite  and  magnetite.  These  minerals  are  admittedly 
the  typical  products  of  contact  metamorphism,  and  their 
nature  and  intergrowth  show  them  to  result  from  the 
action  of  water  above  the  critical  temperature.  This  water 
is  believed  to  have  been  given  off  from  the  hot  magma 
and  to  have  been  accompanied  by  metallic  compounds, 
together  with  sulphur,  fluorine,  etc.  At  a  temperature  of 
+  365°  C.  and  a  pressure  of  200  atmospheres  or  more, 
water  can  only  exist  as  a  perfect  gas.  The  occurrence  of 
the  minerals  mentioned  and  their  manner  of  intergrowth 
show  that  they  were,  in  large  part  at  least,  formed  above 
the  critical  point  of  water,  that  is  under  pneumatolytic  con- 
ditions, and  that  the  sulphides  of  iron,  lead,  zinc  and  cop- 
per are  of  pneumatolytic  origin.  It  has  been  shown  by 
Joseph  Barrell  that  in  certain  cases  the  metamor- 
phism of  the  sediments  is  complete,  and  their  recrys- 
tallization  into  contact  metamorphic  minerals  had  been 
effected  before  the  consolidation  of  the  igneous  magma 
whose  heat  and  vapors  had  caused  the  metamorphism.  In 
such  cases  the  still  fluid  magma  was  giving  off  aqueous 
vapor,  which,  according  to  physicists,  was  above  the  criti- 
cal point,  highly  charged  with  fluorine  and  other  min- 
eralizing agents.  This  has  been  discussed  by  Vogt,  so 
that  detailed  discussion  would  be  out  of  place  now.  The 
subdivisions  of  this  contact  metamorphic  class  are  based 
upon  the  occurrence  of  the  ore  along  the  contact  of  the 
igneous  rock  or  in  beds  upturned  and  extending  some  dis- 
tance from  the  contact,  though  generally  underlaid  by  the 
igneous  rock.  A  recognition  of  the  latter  type  of  deposit 
has  been  made  by  Vogt  and  Beck,  but  no  separate  place 
has  been  assigned  to  it.  Inasmuch,  however,  as  it  has 
been  found  that  the  structural  difference  is  one  of  impor- 
tance, I  have  separated  this  type  and  used  the  term  'bed 
replacement'  as  equivalent  to  the  'strike  deposit'  of  Beck. 
The  individual  types  given  under  each  heading  are  based 
upon  mineralogical  distinctions,  which  are  the  result  of 

—  26  — 


chemical  differences  in  the  mineraHzing  vapors  and  ac-     W.  H.  WEED. 
corded,  therefore,  with  ores  of  different  character. 

Pneumatolytic  Veins. — The  second  class  in  the  group 
of  igneous  emanation  deposits  are  veins  in  which  the 
fissure  has  simply  been  the  channel  for  the  vapors,  and  in 
which  the  impregnation  of  the  country  rock  on  each  side 
of  the  fissure  is  essentially  characteristic.  Pegmatite 
veins  have  been  recognized  as  of  this  general  character, 
and  the  close  relationship  between  pegmatites  and  the 
cassiterite  veins  of  Cornwall  is  quite  well  known.  To 
this  I  would  add  the  veins  characterized  by  tourmaline 
and  copper,  and  those  characterized  by  gold,  pyrite  and 
tourmaline.  The  latter  are,  so  far  as  we  know,  new  in 
the  literature  of  ore-deposits,  and  I  have  but  one  example 
to  present  in  which  the  similarity  to  the  copper  tourma- 
line deposit  is  very  marked,  the  gold  occurring  solely  in 
bunches  of  tourmaline  disseminated  through  aplite,  the 
example  being  near  Helena,  Montana,  at  the  Winscott 
Mine.  Near  Tyson's  Wells,  Arizona,  there  is  a  very 
large  amount  of  gold  ore  of  similar  occurrence,  but  with- 
out the  tourmaline,  the  gold  occurring  in  pyrite,  and  I 
doubt  whether  it  belongs  to  this  class  or  should  be  re- 
ferred to  magmatic  segregations. 

Fiimarolic  Deposits. — The  third  group  of  fumarolic 
deposits  is  of  no  commercial  importance.  It  embraces  de- 
posits of  ferric  chloride,  cuprous  oxide  and  other  metalli- 
ferous minerals  formed  in  clefts  about  volcanic  craters. 
Deposits  of  this  kind  have  been  observed  by  Geikie, 
Fouque  and  other  geologists,  who  have  also  analyzed  the 
gases    given    off    from    these    cavities    and   have    made  ^ 

analyses  of  the  deposits.  They  are  assigned  to  a  separate 
class  because  they  occur  at  the  surface  of  the  earth,  and 
the  veins  are  fumarolic  and  not  pneumatolytic,  as  the  term 
is  used  by  me. 

Gas- Aqueous  Deposits. — The  fourth  group  embraces 
by  far  the  largest  in  number  of  the  commercially  valuable 
ore-deposits  of  the  world.  Ore-deposits  of  this  character 
are  those  which  have  been  commonly  assumed  to  be  due  to 
aqueous  agencies,  and  it  is  well  perhaps  to  emphasize  the 
distinction  to  be  made  between  the  origin  of  these  ore-de- 

—  27  — 


W.  H.  WEED,  posits  as  understood  by  me,  and  the  origin  ascribed  to  them 
by  Prof.  Van  Hise.  According  to  Van  Hise,  ore-deposits 
due  to  aqueous  agencies  are  formed  from  material  gath- 
ered by  circulating  waters  extracting  the  metal  contents 
of  the  rocks  traversed  by  them  and  depositing  this  mate- 
rial after  the  waters  have  been  concentrated  in  trunk 
channels.  While  I  admire  the  brilliant  work  of  Prof. 
Van  Hise  in  explanation  of  the  movements  and  course  of 
underground  waters,  I  believe  that  the  source  of  the 
metals  is  in  most  cases  jto  be  found  in  the  vapors  given  off 
by  the  cooling  igneous  rocks,  and  in  a  minor  degree  to 
leaching  of  the  rigid  differentiated  portions  of  cold  igne- 
ous rocks  by  circulating  waters.  The  difference  is  an 
essential  one,  since  I  believe  that  the  waters  are  to  be  re- 
garded as  the  vehicle,  and  not  the  agent,  and  that  it  is  the 
mixture  of  the  pneumatolytic  gases  with  meteoric  waters 
that  formed  the  metal-bearing  solution. 

This  conception  of  admixed  igneous  vapors  and  mete- 
oric waters  is  not  a  new  one,  but  a  revival  of  the  well- 
known  theory  of  Elie  de  Beaumont  and  Daubree.  It  is 
maintained  that  the  igneous  emanations  which  admittedly 
form  contact  metamorphic  deposits  are  certainly  capable 
of  entering  fissures  traversing  the  cooling  magmas  and 
the  rock  surrounding  them,  where,  although  first  under 
pneumatolytic  pressures,  and  above  the  critical  tempera- 
ture, these  conditions  are  rapidly  modified,  until  reaching 
the  zone  of  circulating  ground-water  the  product  of  igne- 
ous emanations,  both  metallic  and  otherwise,  mix  with 
the  ground-water.  'To  this  combination  of  agencies 
found  in  the  ascending  waters  of  regions  of  igneous  in- 
trusion, the  formation  of  most  metalliferous  veins  is 
probably  due,'  a  final  conclusion  of  Lindgren  ignored 
when  parts  of  the  paper  were  quoted  in  support  of  the 
contention  that  inasmuch  as  most  workable  deposits  were 
formed  by  water,  they  must  have  been  formed  by  water 
originally  meteoric. 

Under  the  head  of  gas  and  water  deposits,  mean- 
ing by  this  title  admixed  gases  and  meteoric  waters, 
I  have  placed  two  classes.  The  first  are  filling  de- 
posits,   in    which    open    fissures    are    filled    by    mineral 

—  28  — 


crusts ;  secondly,  replacement  deposits,  in  which  the  W.  H.  WEK). 
primary  fissure  was  a  minor,  though  very  important, 
structural  feature,  serving  simply  as  the  channel  by  which 
the  solutions  obtained  access  to  the  congenial  rocks  which 
they  replaced.  The  term  'congenial'  is  used  to  imply  a 
rock  which  is  rapidly  replaced  by  the  particular  waters 
acting  upon  them.  At  this  point  a  distinction  might  be 
very  properly  made  upon  the  basis  of  the  chemical  compo- 
sition of  the  waters,  and  I  have  therefore  indicated  the 
subdivisions  given  by  Mr.  Lindgren,  with  which,  in  the 
main,  I  agree.  Inasmuch,  however,  as  the  structural  con- 
ditions which  I  have  indicated  in  his  table  are  not  only  of 
genetic,  but  of  great  practical  importance,  I  have  inserted 
them.  They  are  the  determining  factors  in  the  localiza- 
tion of  the  deposits,  and  if  the  chemical  basis  is  adopted  ^ 
it  would  be  necessary  to  recognize  the  distinctions  a  to  g 
under  precisely  each  one  of  the  chemical  subdivisions 
given. 

Deposits  Formed  by  Meteoric  Waters. — Under  the 
fifth  group,  that  of  meteoric  waters,  I  would  place  those 
deposits  in  which  meteoric  waters  have  taken  the  metals 
in  solution  and  have  carried  them  to  the  place  where  they 
have  become  deposited  as  ores.  This  is  my  conception  of 
the  ore-deposits  formed  according  to  Prof.  Van  Hise's 
theory,  of  which  the  Mississippi  Valley  lead  and  zinc  de- 
posits are,  according  to  his  descriptions,  typical  exam- 
ples. I  do  not  deny  the  great  importance  of  meteoric 
waters,  nor  the  fact  that  such  waters,  when  heated  by 
igneous  rocks,  may  produce  hot  springs,  forming  ore- 
deposits,  but  where  the  hot  spring  waters  owe  their  heat 
to  igneous  rocks,  it  appears  evident  that  they  might  also 
obtain  their  metalliferous  contents  from  the  gases  given 
off  by  such  rocks.  If  this  classification  is  adopted,  it  will 
be  necessary  to  remember  that  transitions  from  one  group 
to  the  other  could  occur,  and  that  when  the  igneous  rocks 
have  solidified  they  are  still  heated ;  that  the  motive  power 
is  furnished  by  them,  and  that  the  leaching  of  such  rocks 
by  the  heated  waters  might  furnish  metalliferous  contents. 

The  sub-group  embraces  sedimentary  deposits,  whose 
character  is   so   well   known   that   it   is    hardly   neces- 


29 


W.  H.  WEED.  sary  to  elaborate  them.  It  is,  however,  wise  to  distinguish 
between  those  which  are  chemical  priecipitates  and  those 
which  are  of  mechanical  origin,  the  first  being  exemplified 
in  the  bog  iron  deposits  and  the  second  in  gold  placers. 

Dynamo-Metamorphic  Deposits. — These  are  similar  to 
contact  deposits  in  mineral  character,  but  show  in  their 
structure  and  mineral  paragenesis  that  they  are  the  result 
of  pressure,  with  a  re-arrangement  and  concentration  of 
material. 

J.  E.  SPURR.  Following    Mr.    Weed,    Mr.    Spurr    said   he   had   no 

need  to  state  his  sympathy  for  the  ideas  which  as- 
signed an  important  part  in  ore  deposits  to  the  action 
of  igneous  magmas,  for,  as  Mr.  Emmons  had  remarked, 
he  had  been  the  first  of  the  members  of  the  Geological 
Survey  to  recognize  the  importance  of  this  agency,  and, 
he  believed,  the  first  among  American  geologists.  In 
1895,  in  his  report  on  the  Mercur  mining  district,  Utah, 
the  observed  facts  had  led  him  to  formulate  the  following 
theories  of  deposition:  First,  that  the  Silver  Ledge  (for 
which  the  camp  was  first  prospected)  was  due  to  the 
action  of  waters  expelled  from  a  porphyry  sheet  during 
the  process  of  cooling,  and  circulating  along  the  contact 
of  the  porphyry  with  limestone.  Second,  that  the  gold 
ores  of  the  Gold  Ledge  (for  which  the  camp  became 
noted)  were  deposited  at  a  subsequent  period  by  vapors 
emanating  from  a  deeper-seated  igneous  body.  Later  on 
he  originated  the  theory  of  ore  deposition  by  siliceous 
magmatic  segregation,  which  was  stated  in  a  report  on 
the  "Geology  of  the  Yukon  Gold  Belt,"  the  field  work  of 
which  was  done  in  1896  and  the  report  written  in  the 
winter  of  1896-7,  while  it  was  not  finally  issued  till  March 
4,  1898.  In  this  report  he  showed  that  the  observed  facts 
in  the  Yukon  region  pointed  clearly  to  the  explanation 
that  the  gold-quartz  veins  of  that  district  were  formed, 
in  part  at  least,  by  direct  siliceous  magmatic  segregation ; 
and  he  suggested  that  the  same  explanation  would  apply 
to  many  other  gold-quartz  veins  in  other  parts  of  the 
world.  Still  later,  in  1900,  in  an  article  on  "Quartz-Mus- 
covite Rock  from  Belmont,  Nevada,  the  Equivalent  of 

—  30  — 


the  Russian  Beresite,"  he  described  his  critical  micro  J.  E.  SPURS 
scopic  studies  on  the  origin  of  the  pecuHar  granitic  dike 
rocks  at  that  locaHty,  and  especially  of  the  blebs., 
segregations  and  veinlets  in  the  rocks,  reaching  the  con 
elusion  that  these  represented  the  final  stage  of  consoli- 
dation of  the  granitic  rock.  He  also  showed  that  the  shaly 
limestone  into  which  these  dikes  are  intrusive  had  been 
metamorphosed  near  the  contact  by  the  same  solutions 
which  had  formed  the  quartz  veinlets  in  the  dikes,  and 
had  become  dense,  hard  siliceous  rocks,  impregnated  with 
iron.  The  suggestion  was  also  added  that  the  ore-bear- 
ing quartz  veins,  found  at  this  very  locality,  which  were 
the  one  feature  he  did  not  have  time  "to  personally  ex- 
amine, were,  to  judge  by  the  already  published  descrip- 
tions of  their  characteristics,  very  likely  another  link  in 
this  chain  of  phenomena,  and  that  the  ores  were  deposited 
at  the  same  time  and  by  the  same  agency. 

All  these  suggestions  were  published  before  the  first 
of  the  papers  in  the  "Transactions  of  the  American  Insti- 
tute of  Mining  Engineers,"  which  had  led  up  to  the  pres- 
ent discussion.  It  was  therefore  naturally  gratifying  to 
find  that  his  views,  in  which  for  a  long  time  he  stood 
alone,  were  coming  to  be  accepted. 

In  1895,  Mr.  Spurr  continued,  he  drew  up  a  genetic 
classification  of  ore-deposits,  which  has  been  slightly 
modified,  with  new  .light,  from,  time  tatime.  The  present 
discussion  has  induced  him  to  present  it  to  the  society. 

Under  the  term  "juvenile  spring"*  deposits,  Mr.  Spurr 
intended  to  classify  ore-deposits  formed  chiefly  by  waters, 
or  waters  and  gases,  expelled  from  consolidating  igneous 
rock,  but  deposited  at  a  distance  from  this  rock. 

The  term  sfygian  deposits  was  offered  as  a  general  ap- 
pellation for  ore-deposits  formed  underground  by  waters 
of  atmospheric  origin. 

The  term  interstitial  deposits  was  adopted  for  the  fill- 
ing of  pores  in  rocks,  in  place  of  the  term  impregnation 


•The  term  originally  proposed  for  this  class  of  deposits  was  solfataric  de- 
posits, but  th'is  was  abandoned  as  suggesting  processes  that  were  not  meant; 
and  the  characterization  by  Prof.  Suess,  in  a  recent  paper,  of  springs  de- 
riving their  water  directly  from  the  exhalations  of  a  solidifying  magma  as 
juvenile  springs,  suggested  the  substituted  term. 

—  31  — 


J.  E.  SPtTKR. 


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32  — 


deposits,  which  had  no  well-defined  meaning,  and  partly      J-  ^^  SPURJC 
of  the  term  disseminated  deposits. 

The  term  Ming  deposits  was  proposed  as  a  general 
name  for  deposits  filling  pre-existing  cavities,  replacing 
the  term  crustiHed  deposits,  proposed  by  Posepny. 

The  term  subsequent  deposits  was  proposed  for  ores 
which  were  not  directly  the  result  of  igneous  processes. 

Regional  metamorphic  deposits  were  put  in  a  separate 
division  by  themselves,  as  being  distinct  both  from  origi- 
nal and  subsequent  deposits. 

It  was  interesting  to  note,  Mr.  Spurr  added,  that  the 
least  important  subdivisions  in  this  classification,  between 
ore-deposits  occupying  spaces  caused  by  rending  and 
those  caused  by  solution,  were  the  primary  divisions  of  ore 
deposits  as  proposed  by  Posepny.  The  next  least  impor- 
tant divisions  in  the  classification,  namely,  replacement, 
interstitial  and  filling  deposits,  had  also  been  regarded  by 
many  as  the  most  important. 

Under  contact  metamorphic  deposits,  Mr.  Spurr  under- 
stood ore-deposits  brought  about  by  the  same  agents 
which  produced  contact  metamorphism  in  general.  These 
agents  were  usually  held  to  be  both  waters  and  vapors 
derived  from  the  cooling  igneous  rock.  He  therefore  be- 
lieved that  ore-deposits  might  be  formed  in  different 
ways  during  the  processes  of  contact  metamorphism,  and 
he  did  not  limit  this  class  of  deposits  to  ores  deposited  by 
gases  alone. 

Defining  his  own  position  in  the  matter  of  theories  of 
ore  deposition,  Mr.  Spurr  said:  I  desire  to  be  classed 
r.either  with  the  ascensionists  nor  the  descensionists,  nor 
any  other  party ;  but  I  stand  now,  as  always,  for  the  prin- 
ciple that  many  different  natural  processes  work  together 
and  singly  to  produce  ore  deposition.  In  my  own  experi- 
ence I  have  never  studied  closely  two  ore-deposits  which 
have  had  exactly  the  same  origin,  and  the  variety  of 
causes  to  which  ore-deposits  have  been  ascribed  in  my 
writings  are  tiie  result  of  careful  study  and  reasoning  in 
each  case,  and  do  not  result  from  vacillations  of  opinion. 
For  example,  I  showed  in  1894  that  the  iron  ores  of  the 
Mesabi  range,  in  Minnesota,  were  the  concentrations  by 


—  3Z 


J.  E.  SPURR.  descending  surface  waters  from  ferruginous  (glauconitic) 
marine  sediments.  In  my  next  important  work,  in  Mer- 
cur,  as  already  stated,  I  ascribed  the  ores  directly  to 
igneous  emanations,  both  gaseous  and  liquid.  In  the 
Aspen  monograph,  I  showed  that  the  ores  had  been 
introduced  from  some  foreign  source  by  ascending  hot 
springs,  such  as  exist  near  Aspen  at  the  present  day. 
In  regard  to  the  Yukon  gold  quartz  veins,  my  arguments 
for  origin  by  siliceous  magmatic  segregation  have  already 
been  mentioned.  Again,  in  describing  the  ores  of  the 
Monte  Cristo  district,  Washington  (ores  of  lead,  zinc, 
copper,  etc.,  containing  silver  and  gold),  I  found  that  the 
balance  of  evidence  favored  the  explanation  that  the  ores 
were  deposited  by  descending  surface  waters  in  Pleisto- 
cene time,  and  that  they  have  been  concentratd  from  a 
disseminated  state  in  the  granitic  rock  (tonalite)  in  which 
most  of  the  veins  occur.  In  a  district  which  I  am  at 
present  studying  (Tonopah)  the  evidence  points  to  a  dif- 
ferent origin  from  any  of  the  foregoing. 

The  solution  of  the  problem  why  we  differ  in  our  con- 
clusions one  from  another  lies  in  the  mental  processes  of 
each.  Most  of  us  see  and  have  seen  the  same  natural 
facts,  but  from  them  we  may  draw  different  conclusions 
or  no  conclusion  at  all.  Just  so  much  of  nature  is  plain, 
to  us  as  we  have  capacity  to  understand.  So  it  seems 
that  the  real  advancement  to  be  made  in  geology  is  not  so 
much  in  searching  after  facts,  which  are  commonplace 
and  easy  of  access,  but  in  examining  and  regulating  our 
reasoning  powers.  There  is  danger  in  the  heedless  appli- 
cation of  purely  theoretical  conclusions  and  hypotheses 
to  concrete  examples.  Such  conclusions,  based  on  physi- 
cal, chemical  or  mathematical  principles,  are  usually  the 
result  of  correct  logic,  but  are  dangerous,  in  that  the 
premises  are  often  assumed.  The  imposing  statement  of 
laws  pertaining  to  a  strange  science  impresses  the  geol- 
ogist, and  he  is  apt  to  believe  that  he  has  hold  of  some- 
thing definite  and  invariable,  which  he  can  apply  as  a 
criterion  in  practical  problems.  Thus  conceptions  like 
those  of  the  zones  of  fracture  and  of  flowage,  the  sea  of 
giound  water,  etc.,  may  be  used  to  decide  questions.  This 


34  — 


IS  illogical,  for  the  conceptions  are  not  fundamental  prin-      J.  E.  SPXJSX, 
ciples  or  axioms ;  and  when  they  are  confronted  by  natu- 
ral phenomena,   independently  interpreted,  one  may  be 
astonished  to  see  how  numerous  and  important  the  excep- 
tions are,  to  say  the  least. 

The  method  of  deduction  from  preconceived  theories, 
then,  which  led  many  of  the  by-gone  geologists  into  error, 
has  become  replaced  by  the  method  of  logical  inference 
from  observed  facts,  to  which  the  actual  progress  of 
geology  is  chiefly  due.  Undoubtedly  this  latter  is  what 
one  should  strive  to  stick  to.  He  should  collect  facts, 
assemble  them,  group  them,  and  note  the  conclusions  to 
which  they  point.  This  last  stage  in  the  process  is  all- 
important,  and  one  of  which  the  impartial  carrying  out 
marks  the  properly  balanced  scientist.  Too  often  the  con- 
servative geologist  assembles  the  facts,  yet  fails  to  note 
their  meaning,  or,  if  this  is  partly  forced  upon  him,  in  spite 
of  himself,  he  refuses  to  recognize  it,  with  a  clinging  to 
what  is  old  and  a  distrust  of  the  novel,  even  though  he 
may  be  rejecting  the  truth  and  harboring  the  error. 

While,  therefore,  the  method  of  observation  and  infer- 
ence should  be  carefully  applied  to  geological  problems, 
and  we  must  ever  beware  of  forcing  facts  to  suit  our  pre- 
conceived theories,  yet  it  must  be  remembered  that  no  man 
can  go  beyond  his  own  mental  depth  in  this  process.  It  is 
a  fundamental  principle  in  logic  that  one  cannot  under- 
stand a  conclusion  or  a  law  with  whose  elements  he  is 
not  already  acquainted.  It  is  entirely  a  matter  of  the 
thinker,  not  of  the  facts  investigated.  An  Arabic  word 
leaves  a  blank  in  the  mind  of  a  Chinaman.  You  cannot 
argue  with  a  cow,  nor  talk  geology  to  a  coal-heaver.  To 
narrow  down  the  application,  a  chain  of  logic  and  infer- 
ence, based  upon  physical  and  mathematical  grounds  and 
pointing  to  a  certain  conclusion,  makes  no  impression  on 
the  mind  of  the  average  geologist.  If  he  accepts  the  con- 
clusion, he  does  it  because  of  the  reputation  of  the  arguer, 
and  not  because  of  the  argument.  Again,  a  line  of  argu- 
ment based  upon  the  behavior  of  rock  magmas  during  the 
process  of  crystallization  makes  no  impression  on  one  who 
is  unacquainted  with  this  department  of  knowledge.  Thus 


—  35  — 


J.  E.  SPURR.  the  correct  process  for  the  geologist  resolves  itself  into 
the  following:  Preconceived  theories  for  a  special  prob- 
lem should  be  avoided,  and  the  solution  of  the  problem 
should  be  logically  inferred  from  local  facts;  but  the 
worker  must  have  a  broad  knowledge  of  possibilities,  else 
the  conclusion  will  utterly  escape  him. 

These  remarks  may  not  seem  germane  to  the  discus- 
sion, but  I  hold  that  they  are  the  root  of  the  matter. 
Illustrations  are  frequent  and  striking.  Let  a  geologist 
bring  out  forcibly  the  principle  of  concentration  of  pre- 
existing ores  by  descending  waters,  and  everybody  sees 
cases  of  'secondary  enrichment.'  The  facts  were  there 
before,  but  everybody  could  not  see  what  they  meant, 
because  they  had  no  foreknowledge  of  the  principle.  Thus 
improperly  balanced  minds  permit  this  foreknowledge  to 
distort  objective  impressions,  and  so  they  see  enrichment 
of  this  sort  where  none  exists.  Let  the  geologist  and  the 
mining  engineer,  then,  with  the  principles  of  the  present 
discussion  in  mind,  investigate  and  review  both 
mine  and  literature,  and  a  still  closer  agreement, 
and  a  steadier  progress  in  real  knowledge  may  be  ex- 
pected. 

W.  LINDGREN.  ^^^'  Spurr  was  followed  by  Mr.  Waldemar  Lindgren, 

who  said:  A  genetic  classification  is  surely  a  great 
desideratum  in  the  science  of  ore-deposits,  and  it 
seems  as  if  we  had  arrived  at  a  point  where 
such  a  scheme  might  be  tentatively  advanced  with 
profit,  although,  in  view  of  the  great  diversity  of 
opinion  which  still  exists  among  prominent  mining  geol- 
ogists, a  general  acquiescence  in  any  one  certain  system 
is  not  to  be  expected  for  some  time  to  come.  The  classifi- 
cations of  Messrs.  Weed  and  Spurr  are  based  on  general 
principles,  which,  according  to  my  view,  are  perfectly 
sound,  and  which  I  ventured  to  emphasize  in  1900,  at  a 
time  when  the  theory  of  almost  exclusive  concentration 
by  atmospheric  waters  found  few  opponents  in  this  coun- 
try. I  still  adhere  to  the  opinion  that  the  majority  of  the 
metalliferous  veins  of  the  Cordilleran  belts  are  due  to  gas- 
eous emanations  from  intrusive  magmas,  released  by  de- 

-36- 


creasing  pressure,  mingling  with  surface  waters  and  as-  w.  LINDGREN. 
cending  as  hot  springs.  Deposits  exclusively  due  to  at- 
mospheric waters  are  no  doubt  very  numerous,  but  chiefly, 
I  believe,  contain  the  more  abundant  metals,  such  as  iron 
and  copper.  It  cannot  be  denied  that  many  of  the  argu- 
ments advanced  by  Professor  Kemp  and  others  against  the 
extent  and  depth  of  the  underground  circulation  of  atmos- 
pheric waters  are  very  strong  and  tend  to  diminish  the 
universal  application  of  Professor  Van  Hise's  theory. 
It  is  unnecessary  to  discuss  this  problem  here,  since  Mr. 
Kemp  has  taken  up  this  question  in  considerable  detail. 
The  small  amount  of  water  in  deep  mines  is  certainly  re- 
markable. I  shall  always  remember  my  intense  surprise, 
when  visiting  Przibram  in  1881,  to  find  the  1000  meter 
level  of  the  Adalbert  shaft,  not  only  dry,  but  actually 
dusty.  I  would  also  like  to  call  attention  to  the  fact  that 
in  very  dry  regions,  like  Arizona,  rain  water  may  remain 
for  several  months  to  a  depth  of  several  feet  in  shallow 
shafts,  while  the  water  level  of  the  country  stands  sev- 
eral hundred  feet  lower. 

Regarding  the  details  of  the  schemes  proposed  and  the 
assignment  by  Mr.  Weed  of  the  various  types  of  deposits, 
there  may  naturally  be  varying  views,  and  indeed  I  under- 
stand that  Mr.  Weed  considers  these  details  as  in  part 
provisional.  The  first  group  of  magmatic  segregations 
contains  the  recognized  groups  of  titanic  ores  and  chro- 
mite,  to  which  may  be  added  some  nickel  deposits;  but 
workable  copper  deposits  belonging  beyond  reasonable 
doubts  to  this  type  are  not,  I  believe,  thus  far  recog- 
nized. 

The  class  of  siliceous  magmatic  segregations  is  ear- 
nestly advocated  by  Mr.  Spurr  and  recognized  by  Mr. 
Weed  by  three,  to  my  mind,  very  doubtful  examples. 
Though  admitting  that  quartz  veins  of  this  origin  exist, 
I  do  not  consider  that  proofs  have  been  brought  to  show 
that  they  contain  payable  gold  ores,  and  would,  from  my 
standpoint,  strongly  object  to  class  the  normal  gold- 
quartz  veins  under  this  heading.  They  may  very  well  be 
due  to  what  Prof.  Vogt  aptly  calls  eruptive  after-effects, 
but  not,  I  think,  to  direct  magmatic  segregation.     The 


37 


W.  LINDGREN.  distinction  between  these  two  things  should  be  empha- 
sized. The  latter  takes  place  in  a  mass  of  fused  material, 
with  or  without  the  presence  of  a  subordinate  amount  of 
water;  the  former  involves  entirely  predominating  aque- 
ous solutions  or  gases.  It  is  admitted  that  there  may  be 
an  intermediate  stage  between  the  two  conditions;  and 
possibly  the  pegmatite  veins  may  have  been  formed  by 
magmas  exceedingly  abundantly  charged  with  HoO,  or 
with  H2O  having  an  exceedingly  large  amount  of  matter 
in  solution.  As  stated  above,  1  ao^ree  with  Messrs.  Weed 
and  Spurr  in  believing  that  a  very  large  number  of  fis- 
sure veins  are  formed  by  the  mingling  of  atmospheric 
waters  with  ascending  emanations  from  cooHng  intrusive 
magmas.  Among  these  emanations  I  believe  that  water 
prevails,  but  that  along  with  it  large  amounts  of  CO^, 
H^S,  and  heavy  metals  in  various  combination  are  also 
brought  up.  In  a  forthcoming  report  on  the  Clifton  Cop- 
per District  in  Arizona,  I  hope  to  produce  convincing 
proof  of  the  direct  causal  connection  of  certain  fissure 
veins  with  certain  intrusive  masses,  and  further  bring  di- 
rect evidence  of  the  high  temperature  at  which  they  were 
deposited. 

The  unimportant  group  of  the  fumarolic  deposits, 
recognized  by  Messrs.  Weed  and  Spurr,  I  would  pass 
over  with  the  remark  that  they  are  justly  separated  from 
the  contact  metamorphic  or  pneumatolytic  division.  It 
has  long  been  my  opinion  that  the  words  fumarolic  and 
pneumatolytic  should  be  applied  to  different  things,  and 
this  view  was  expressed  a  few  months  ago  in  a  paper  on 
the  gold  production  of  this  continent.  Fumarolic  emana- 
tions are  vapors  liberated  from  cooling  magmas  near  the 
surface  under  slight  pressure.  It  is  true  that  the  word 
pneumatolytic  was  first  used  by  Bunsen  in  a  general  sense 
to  cover  all  gaseous  emanations  from  magmas,  but  as 
modified  by  Broegger  and  used  by  most  modem  writers,  it 
has  come  to  be  applied  to  the  action  of  perfect  gases,  that' 
is,  to  substances  above  their  critical  temperature  and  pres- 
sure. If  this  definition  is  not  accepted  it  would  be  better 
to  adopt  a  new  term  for  this  conception. 

—  38  — 


This  brings  us  to  the  group  of  the  contact  metamor-  W.  LINDGREN. 
phic  deposits,  which  Messrs.  Weed  and  Spurr  both  recog- 
nize as  a  prominent  group.  I  beHeve  I  am  not  mistaken 
in  saying  that  this  class  of  deposits  will  be  better  known 
and  its  extent  better  realized  a  few  years  from  now.  Al- 
ready the  examples  are  multiplying  and  some  important 
old  mines  are  shown  to  belong  to  this  division. 

We  are  all  agreed  that  the  subject  which  has  occupied 
our  attention  this  evening  is  one  of  great  difficulty  and 
complexity,  as  always  must  be  the  case  with  questions  re- 
lating to  processes  going  on  in  a  region  concerning  which 
we  have  but  little  direct  information — that  is,  below 
the  surface  of  the  earth.  It  seems  to  me,  however,  that 
the  only  way  in  which  the  question,  relating  to  the  direct 
emanation  of  metallic  substances  from  igneous  magmas, 
can  be  determined  is  by  the  careful  study  of  the  contact 
metamorphic  deposits  and  the  igneous  rocks  which  have 
produced  them.  We  have  here  metallic  minerals  de- 
posited in  such  intimate  intergrowth  with  contact  meta- 
morphic minerals  that  their  simultaneous  origin,  in  cases 
where  no  subsequent  alteration  has  taken  place,  can 
not  for  a  moment  be  doubted.  The  direct  relation  of 
contact  metamorphism,  to  the  igneous  rocks  which  in- 
duce it,  has  long  been  a  well-known  fact  to  petrographers, 
and  the  minerals  we  find  in  ore-deposits  of  this  type  are 
characteristically  those  which  the  world  over  are  formed 
in  sediments  near  bodies  of  intrusive  rocks.  The 
association  is  that  of  garnet,  epidote,  wollastonite  and 
andalusite,  with  magnetite,  specularite,  bornite,  pyrite, 
chalcopyrite,  zincblende  and  other  simple  sulphides.  The 
complex  sulphosalts,  such  as  the  sulphantinionites,  are 
not  known,  but  tellurides  occur  in  places,  as  shown  by  Mr. 
Weed.  The  action  is  always  most  intense  at  limestone 
contacts,  while  shales  and  sandstones  are  affected  in  a  less 
extensive  degree.  Andalusite  and  epidote  have  not  as  yet 
been  artificially  reproduced  by  dry  fusion  or  in  the  wet 
way ;  garnet  and  wollastonite  only  exceptionally  by  aid  of 
chlorides  and  fluorides  as  mineralizing  agents.  Gar- 
net, andalusite  and  wollastonite  do  not  seem  to  be  formed 
in  nature  by  water  except  at  high  temperature.      In  the 


—  39' 


W.  LINDGREN.  artificial  reproduction  of  minerals  it  has  been  found  that 
certain  substances  act  as  'mineralizing'  agents/  that  is, 
facilitate  the  crystallization  of  minerals  not  easily  ob- 
tainable without  them.  They  do  not  necessarily  enter 
into  the  combination  formed.  Thus  at  comparatively  low 
temperature  sodium  carbonate  facilitates  the  formation 
of  certain  sulphides.  These  mineralizing  agents  act  most 
energetically  at  high  temperatures;  among  them  are  cer- 
tain volatile  compounds  of  silica,  fluorine,  tungsten,  chlor- 
ine, boron  and  zirconium;  and  last  but  not  least,  simple 
water  at  a  high  temperature,  the  action  of  the  latter  ap- 
parently increasing  at  least  up  to  its  critical  temperature. 
It  seems  probable  that  water  at  a  very  high  temperature 
is  necessary  to  produce  the  typical  contact  metamorphic 
silicates.  With  the  ordinary  increase  in  temperature  in 
depth  (i"  per  30  meters)  water  would  certainly  be  above 
the  critical  temperature  (+365*  C.)  at  a  depth  of  11,000 
meters,  and  the  requisite  pressure  (200  at.)  would  be  ob- 
tained even  under  hydrostatic  conditions  at  2,000  meters. 
Under  circumstances  of  intrusion  at  the  latter  depth  the 
temperature  at  the  contact  would  be  at  least  1,200**  C.  and 
would  surely  continue  above  365*  for  long  periods.  Un- 
der such  circumstances  water  could  only  exist  as  a  gas 
along  the  contact. 

The  mere  diffusion  of  heat  is  slow  and  it  would  take 
many  years  to  produce  a  temperature  of  365°  at  a  dis- 
tance 100  feet  away  from  the  supposed  contact.  But 
conditions  change  when  we  consider  that  the  intrusive 
rock  contained  dissolved  gases  of  various  kinds,  among 
which  water  above  the  critical  temperature  predomin- 
ated. The  intrusion  cracked  and  shattered  the  surround- 
ing cold  rock,  and  through  the  fissures,  as  well  as  through 
the  pores  of  the  rock,  these  hot  gases  rapidly  pressed 
outward,  enormously  increasing  the  heated  zone  and  the 
zone  in  which  chemical  action  was  produced.  The  very 
varying  width  of  the  contact  metamorphic  zone  in  differ- 
ent rocks  seems  to  confirm  this  view.  The  intensity  of 
metamorphism  is  in  proportion  to  the  amount  of  the 
gases  contained  in  the  magma  and  to  the  shattering  and 
porosity  of  the  surrounding  rock.    We  have  to  admit  that 


in  many  cases  temperature  above  370*  C.  must  prevail      W.  LINDGREN. 
perhaps  hundreds  or  even  thousands  of  feet  from  the  con- 
tact, and  consequently  the  water  must  be  in  the  gaseous 
state. 

But  many  intrusions  doubtless  take  place  at  less  depth 
than  2,000  meters,  and  in  this  connection  it  should  be 
emphasized  that  for  intrusive  conditions  it  is  wholly  in- 
admissible to  calculate  the  pressure  from  hydrostatic  con- 
ditions. The  forming  of  laccoliths,  which  may  certainly 
take  place  less  than  2,000  meters  below  the  surface,  in- 
volves an  enormous  stress  and  I  maintain  as  probable  that 
in  most  cases  the  pressure  all  along  intrusive  contacts  far 
exceeds  200  atmospheres. 

All  this  presupposes  that  the  active  agent  is  pure 
water.  As  a  matter  of  fact,  we  actually  have  water 
charged  with  gases  and  other  substances.  The  critical 
temperature  of  this  mixture  is  not  known,  but  is  probably 
not  greatly  different  from  that  of  water.  Carbonic  diox- 
ide, hydrogen  sulphide  and  many  combinations  of  fluor- 
ine, boron  and  chlorine  have  low  critical  temperatures 
and  pressures  and  would  certainly  exist  as  perfect  gases 
under  the  conditions  promised.  There  is  still  another 
point  in  connection  with  this  that  I  would  like  especially 
to  emphasize  at  this  time;  in  the  existing  text-books  on 
geology  and  petrography,  we  frequently  find  it  stated 
that  during  contact  metamorphism  the  altered  rocks  have 
received  no  important  addition  of  substance.  From  recent 
studies  of  contact  metamorphism  in  the  United  States, 
this  statement  should  probably  be  greatly  modified.  It 
may  be  true  that  in  many  cases  there  has  been  but  little 
additional  substance,  and  that  the  metamorphism  has 
simply  been  effected  by  the  molecular  re-arrangement  of 
minerals  by  the-  means  of  fluid  or  gaseous  water.  In 
other  cases,  however,  the  indications  are  plain  that  an- 
enormous  amount  of  material  has  been  given  off 'by  the 
magma.  During  a  recent  examination  of  the  Clifton 
copper  mines  in  Arizona,  where  extensive  contact  meta- 
morphism has  taken  place  in  the  limestones  adjoining  an 
intrusive  diorite  porphyry,  some  interesting  relations  have 
been  observed.    At  the  contact  with  granite  or  quartzite, 

—  41  — 


W.  LINDGREN. 


no  alteration  is  observed.  At  the  contact  with  Hmestones, 
however,  garnet  and  epidote  develop  on  a  large  scale,  and 
are  associated  with  pyrite  and  chalcopyrite.  There  is  a 
total  thickness  of  about  800  feet  of  limestone.  The  lower 
part  of  the  series  is  very  siliceous,  and  the  only  pure  car- 
bonate of  lime  is  found  in  some  50  feet  of  the  upper  part 
of  the  series  belonging  to  the  lower  Carboniferous.  The 
most  extensive  and  complete  contact  metamorphism  has 
taken  place  in  this  stratum  of  pure  limestone.  It  has, 
over  a  large  area,  been  almost  entirely  converted  to  lime- 
iron  garnet,  associated  with  some  epidote  and  a  little 
copper  sulphide.  This  action  clearly  implies  an  enormous 
transfer  of  silica  and  iron  from  the  cooling  porphyry  to 
the  limestone. 

Evidence  from  several  other  points  tends  at  present  in 
the  same  direction.  I  consider  it  practically  proved  that, 
under  certain  circumstances,  cooling  magmas  will  give  off 
quantities  of  various  substances,  such  as  water,  silica,  iron, 
metallic  sulphides,  and,  in  small  quantities,  fluorine  and 
boron  compounds.  Important  results  regarding  the  gene- 
sis of  ore-deposits  will,  I  think,  come  from  further  study 
of  these  deposits.  In  many  cases  it  wilUbe  impossible  to 
prove  the  relative  parts  which  the  atmospheric  and  the 
igneous  waters  play  in  the  formation  of  a  given  ore-de- 
posit, but  I  believe  that,  on  the  whole,  the  path  for  future 
advancement  is  laid  in  the  direction  indicated  above. 


S.  F.  EMMONS. 


On  February  25,  at  another  meeting  of  the  Geological 
Society  of  Washington,  held  at  the  Cosmos  Club,  the 
subject  of  a  generic  classification  of  ore-deposits  was 
again  made  the  topic  for  discussion.  Mr.  C.  W.  Hayes 
presided. 

The  discussion  was  opened  by  Air.  Emmons,  who  said : 
At  the  meeting  of  January  14,  a  discussion  was  com- 
menced on  genetic  classification  of  ore-deposits,  a  discus- 
sion which  could  not  be  completed  because  of  the  limited 
time,  and  further  because  several  of  our  members  who 
were  entitled  to  speak  with  great  authority  on  the  subject 
were  not  present ;  and  it  is  proposed  at  the  present  meeting 
to  resume  the  discussion  and  to  give  an  opportunity  for 

—  42  — 


those  members  to  express  their  views.  It  was  not  S.  F.  EMMONS^ 
supposed  at  the  start  that  a  purely  genetic  classification 
would  be  one  that  could  be  adopted  in  practical  work, 
and  many  of  us  feel  that  we  know  as  yet  too  little  about 
ore  genesis  to  attempt  such  a  classification  as  would  have 
any  finality ;  but  we  do  feel  that  the  presenting  of  one  or 
more  tentative  schemes  on  this  basis  will  have  a  useful 
effect  in  clarifying  our  ideas,  in  promoting  an  interchange 
of  views,  and  perhaps  also  in  helping  us  in  our  field  ob- 
servations by  indicating  phenomena  that  it  is  important 
to  recognize  in  the  course  of  underground  studies. 

Two  tentative  classifications  were  proposed,  at  the 
previous  meeting  by  Messrs.  Weed  and  Spurr,  in  which 
the  authors  have  given  much  greater  importance  to  the 
direct  action  of  eruptive  agencies  in  producing  ore-de- 
posits than  has  hitherto  been  ascribed  to  them  by  most 
American  writers  on  the  subect.  The  question  of  the 
ultimate  origin  of  the  metallic  minerals  which  go  to  make 
up  our  workable  ore-deposits  is  one  which  involves  much 
that  is  purely  speculative  and  beyond  the  reach  of  actual 
proof  or  demonstration  in  the  field.  Moreover,  it  has 
been,  as  I  conceive,  a  characteristic  of  American  investi- 
gators on  ore-deposits,  as  contrasted  with  their  European 
colleagues,  that  they  have  based  their  conclusions  with 
regard  to  genesis  more  on  actually  observed  facts  in  the 
field  than  on  laboratory  studies  and  theoretical  reasoning. 
For  instance,  as  a  pupil  of  Elie  de  Beaumont,  I  was  taught 
that  vein  formations  were  the  result  of  emanations  from 
igneous  rocks  under  the  influence  of  certain  mineralizing 
agents — the  dying  phases  of  eruptive  activity.  When, 
however,  I  took  up  the  study  of  ore-deposits  in  the  field, 
applying  to  that  study  the  methods  employed  in  the  ob- 
servation of  other  geological  phenomena,  and  endeavor- 
ing to  keep  my  mind  free  from  the  bias  of  any  precon- 
ceived theories,  I  failed  for  a  long  time  to  find  any  evi- 
dence that  would  support  the  igneous  emanation  theor}' 
in  the  deposits  I  had  opportunities  of  studying.  In  the 
condition  in  which  they  were  then  found,  they  appeared 
to  me  evidently  the  result  of  concentration  by  circulating 
waters.    As  to  their  ultimate  origin,  I  conceived  that  the 


—  43 


S.  F.  EMMONS.  greater  part  had  probably  been  brought  within  reach  of 
these  circulating  waters  by  igneous  ma^as  as  fhey  pro- 
ceeded upwards  from  the  interior  of  the  earth,  but  that 
these  magmas  had  cooled  and  consolidated  before  the  con- 
centrations had  taken  place,  since  the  rock-fractures  which 
had  afforded  the  trunk  channels  for  the  concentrating  so- 
lutions were  in  most  cases  subsequent  to  that  consolida- 
tion. In  more  recent  years,  when  our  field  of  study  has 
widened  and  the  number  of  workers  (lamentably  few  in 
the  early  days)  has  greatly  increased,  actual  field  demon- 
stration has  become  available  that  a  certain  class  of  de- 
posits are  probably  the  result  of  direct  emanations  from 
cooling  igneous  rocks,  and  others  may  be  actual  segrega- 
tions in  an  igneous  magma  during  the  process  of  cooling. 
Such  practical  demonstrations  of  views  that  previously 
rested  upon  an  almost  theoretical  basis  have  naturally  ex- 
cited great  interest  among  students  of  ore-deposits,  and  it 
is  eminently  desirable  that  their  field  should  be  as  widely 
extended  as  possible.  On  the  other  hand,  it  is  wise  to 
guard  oneself  against  the  attractiveness  of  what  appears 
to  be  novel,  and  hence  presumably  an  advance  on  pre- 
viously conceived  ideas,  and  not  to  confound  speculative 
assumption  with  demonstration.  Herein  lies  an  actual 
danger  in  the  effect  of  this  kind  of  speculation.  Men 
may  be  led  to  assume  for  a  given  ore-deposit,  with  regard 
to  whose  genesis  they  have  really  no  direct  evidence,  an 
origin  that  accords  with  the  latest  speculative  views,  and 
such  assumption  may  later  acquire  the  standing  of  a  dem- 
onstration. 

Some  of  the  instances  which  both  Weed  and  Spurr 
quote  as  examples  of  the  class  of  siliceous  magmatic 
segregations  come  under  this  head.  I  have  particularly  m 
mind  the  quartz  veins  of  Belmont,  Nev.,  quoted  by  Mr. 
Spurr,  since  his  statement  is  based  upon  my  own  obser- 
vations made  as  far  back  as  1868.  While  I  should  be 
unwilling  to  state  from  a  recollection  of  so  far  distant 
observations  that  such  an  origin  is  impossible,  Mr. 
Spurr's  statement  is  purely  speculative,  since  he  could  not 
examine  the  veins  in  question ;  yet  they  are  very  likely  to 
be  quoted  by  some  later  writers  as  examples  of  this  very 


—  44  — 


doubtful  class,  in  the  same  manner  as  Weed  has  quoted     S.  F.  EMMOITS. 

Spurr's  Alaskan  quartz  segregations,  of  whose  origin  the 

latter  seems  to  have  equally  little  demonstrable  proof. 

Whether  it  is  justifiable  to  extend  pneumatolytic  agencies 

as  far  as  these  gentlemen  have  done  depends  primarily 

upon  a  question  which  it  seems  difficult  to  bring  within 

the  range  of  actual  or  even  experimental  demonstration; 

namely,  whether  igneous  magmas  as  they  come  from  the 

.interior  of  the  earth  contain  sufficient  water  to  produce  the 

phenomena  observable  in  our  ore-deposits. 

In  a  recent  paper  on  Hot  Springs,  Prof.  Edward 
Suess,  the  eminent  geologist  of  Vienna,  takes  the  affirma- 
tive side  of  this  question,  dividing  hot  springs  into  those 
whose  waters  rise  under  hydrostatic  pressure,  and  those 
that  derive  their  waters  from  the  interior  of  the  earth, 
the  latter  being  characterized  by  their  intermittence.  Witri 
regard  to  the  steam  emanating  from  volcanic  eruptions, 
he  comes  to  the  following  conclusion: 

"Volcanoes  are  not  fed  by  the  infiltration  of  ocean 
water,  but  ocean  water  receives  additions  to  its  volume 
by  eveiry  (volcanic)  eruption." 

Prof.  J.  F.  Kemp,  of  Columbia  College,  has  been  tht? 
first  among  American  writers  on  ore-deposits  to  argue  in 
favor  of  the  sufficiency  of  the  supply  of  water  that  may 
be  furnished  by  eruptive  magmas,  and  we  shall  be  glad  to 
learn  from  him  any  facts  that  may  bear  upon  this  ques- 
tion. 

Prof.  Kemp  said:  The  early  schemes  for  the  classi-  jas.  f.  kemp. 
fication  of  ore-deposits  were  chiefly  based  on  shape 
and  texture,  after  the  fundamental  difference  between  in- 
terbedded  deposits  and  veins  in  fissures  had  been  once  es- 
tablished ;  but  as  time  has  gone  on  principles  of  origin  have 
come  more  and  more  to  the  front.  It  is  now  a  question  of 
the  relative  importance  which  is  to  be  assigned  to  geo- 
logical structure  on  the  one  hand  and  to  source  of  ore  and 
agent  of  introduction  on  the  other.  Geological  structure  is 
generally  safe  and  involves  less  assumption,  but  as  regards 
derivation  and  agent  we  are  now  in  a  position  to  speak 
in  some  instances  with  assurance.    While  in  the  past  at- 

—  45  — 


JAS.  F.  KEMP,  tention  has  been  specially  directed  toward  the  normal  cir- 
culation of  ground-waters  of  meteoric  origin,  more  re- 
cently we  have  had  emphasis  placed  especially  on  the 
igneous  phenomena.  To  Messrs.  Lindgren  and  Weed 
we  owe  a  great  debt  in  this  particular,  and  especially  to 
the  latter  for  the  formulation  of  the  scheme  of  classification 
.under  discussion. 

As  a  general  principle,  groups  in  schemes  of  classifica- 
tion should  be  based  upon  certainties,  and,  so  far  as  pos- 
sible, should  not  be  capable  of  two  interpretations.  We 
may  set  aside  the  group  of  igneous  magmatic  segrega- 
tions, as  a  type  whose  origin  admits  of  no  argument. 
Titaniferous  iron  ores  are  its  most  important  representa- 
tive. Corundum  and  chromite  are  known  in  the  same 
relations.  That  the  pyrrhotite-chalcopyrite  ores  are  of 
this  type  is  doubtful,  as  has  been  shown  by  Lindgren  for 
those  at  Rossland,  and  recently  for  the  Sudbury  ores  by 
one  of  my  students,  C.  W.  Dickson,  in  a  thesis,  which  was 
read  before  the  American  Institute  of  Mining  Engineers 
at  the  Albany  meeting. 

At  the  other  extreme  we  may  also  set  aside  the  super- 
ficial placers  and  related  residual  deposits,  since  they  in- 
volve no  uncertainties.  For  the  rest  we  may  start  with 
contact  deposits,  especially  as  produced  by  the  action  of 
eruptives  on  limestones;  and  with  pegmatites,  which  are' 
certainly  the  effects  of  expiring  igneous  phenomena.  We 
pass,  from  these  points  of  departure,  through  veins  and 
other  forms  of  ores,  and  reach  the  undoubted  results  of 
deposition  from  meteoric  waters  at  the  other  extreme. 
In  the  interval  between  the  extremes,  where  doubt  arises 
as  regards  interpretation,  it  is  best  to  fall  back  on  the  as- 
sured facts  of  attendant  geological  structure  as  the 
foundation  of  the  type. 

It  is  strange  that  the  importance  of  contact  zones  of 
garnet,  vesuvianite,  wollastonite,  epidote  and  copper  ores 
with  gold  have  gone  so  long  without  appreciation  of 
their  true  nature.  Although  for  some  years  correctly 
interpreted  in  Norway  and  described  in  the  Norwegian 
reports,  Mr.  Lindgren's  paper  on  the  ores  of  the  Seven 
Devils  District  of  Idaho,  and  of  others  of  related  charao 

—  46  — 


ter,  first  brought  them  to  American  attention,  but  we  have  JAS.  F.  K£MP« 
learned  of  many  since,  as  at  Cananea  and  San  Jose,  in 
Old  Mexico,  and  San  Pedro,  New  Mexico.  With  the  last 
two  I  am  most  familiar,  and  at  each  there  are  acres  of 
\garnet  rock  which  has  been  produced  from  nearly  pure 
limestone  by  the  addition  of  silica  from  the  eruptive,  un- 
doubtedly while  highly  heated.  The  change  at  Cananea  .  ^ 
and  San  Pedro  has  followed  individual  beds  for  long  dis- 
tances, and  no  one  can  fail  to  be  impressed  with  the  enor- 
mous amount  of  silica  which  has  been  supplied  in  con- 
nection with  watery  vapor  or  its  dissociated  gases  and 
probably  other  mineralizers.  Had  not  this  silica  been 
caught  and  locked  up  near  the  eruptive,  as  it  would  not 
have  been  in  walls  of  almost  any  rock  other  than  lime- 
stone, we  would  have  had  very  great  veins  produced  in 
overlying  strata.  This  is,  in  my  opinion,  the  method  by 
which  many  veins  have  been  formed,  even  though  the 
stimulating  eruptive  is  not  exposed  to  sight. 

I  have  recently  had  the  privilege  of  reading  a  very 
valuable  contribution,  recently  issued,  upon  the  "Gold 
Deposits  of  North  America,"  by  Mr.  Lindgren,  and 
submitted  to  the  American  Institute  of  Mining  Engi- 
neers. In  it  he  shows  that  after  several  geological  periods 
— it  may  be  even  after  geological  eras — of  no  vein  for- 
mation, the  latter  suddenly  and  for  a  brief  period  became 
very  active,  following  igneous  outbreaks.  It  then  died 
away.  Lindgren  attributes  the  activity  to  the  eruptive 
rock,  and  I  think  he  is  right.  Eruptive  rocks  certainly 
accompany  great  upheavals,  and  extensive  fracturing, 
and  some  may  claim,  with  more  or  less  reason,  that  they 
have  merely  furnished  the  propelling  energy  and  the  vein- 
minerals  to  circulating  meteoric  waters,  but  I  incline 
rather  to  believe  them  not  only  the  source  of  the  energy 
and  the  minerals,  but  largely  of  the  watery  vehicle  itself, 
a  view  that  has  claims  to  confidence,  equal,  if  not  superior, 
to  those  put  forth  for  meteoric  waters.  Thus  we  find 
no  vein-formation  through  enormous  extent  of  time  when 
conditions  were  favorable  to  meteoric  waters,  and  suddenly 
the  outbreak  of  eruptive  rocks  starts  it  up.  I  am  therefore 
in  full  sympathy  with  the  tendency  shown  in  Mr.  Weed's 

—  47  — 


JASs  F.  KEMP,  scheme  of  classification,  and  with  the  importance  placed 
by  it  upon  the  igneous  factors. 

It  may  also  be  said  that  outbreaks  of  eruptives  and 
great  upheavals  imply  extensive  fracturing  of  the  rocks, 
and  are  thereby  favorable  to  the  circulation  of  meteoric 
waters,  which,  following  down  the  fractures,  gather  up 
their  burden  of  ore  and  gangue,  and  return  to  the  surface 
perhaps  being  expelled  by  the  heat  of  the  eruptive.  The 
period  of  vein  formation  would  then  last  until  the  cavities 
were  plugged  and  the  meteoric  waters  no  longer  found  en- 
trance or  exit. 

There  are,  however,  certain  other  general  objections  to 
attaching  this  relatively  great  importance  to  the  meteoric 
waters  as  against  the  emissions  of  eruptive  rocks.  Thus 
fractured  districts  without  eruptive  rocks,  or  fractured  dis- 
tricts in  old  and  long  cooled  eruptives,  are  not  uncommon, 
and  yet  extensive  vein  formation,  while  not  unknown,  is 
rarely  seen.  Meteoric  waters  are  everywhere  available, 
except  in  the  arid  districts,  and  the  materials  of  the  or- 
dinary gangue  minerals,  such  as  silica,  lime,  and  iron,  are 
the  universal  elements  of  rocks ;  but  vein  formation  as  a 
matter  of  experience  is  rare.  This  operates  to  diminish 
the  probability  of  the  efficient  action  of  meteoric  waters, 
and  throws  toward  the  agent,  which,  almost  without  ex- 
ception, visibly  accompanies  vein  formation,  the  greater 
weight  of  importance.  What  was  a  coincidence,  conse- 
quently rises  to  the  dignity  of  a  cause. 

If  now  an  observer,  greatly  impressed  by  the  extensive 
alterations  and  chemical  changes  wrought  by  meteoric 
waters  in  those  portions  of  the  crust  of  the  earth  which 
stand  above  the  ground- water  level  and  which  are  subject 
to  a  heavy  rainfall,  and  still  more  by  the  extensive  con- 
centrations produced  in  the  case  of  that  most  abundant 
and  soluble  of  the  metals,  iron — if  this  observer  were  to 
plead  the  cause  of  the  meteoric  waters  for  ore-deposits  in 
general,  he  would  naturally  proceed  as  follows.  And  to 
him,  a  believer  in  the  greater  efficiency  of  the  igneous 
rocks  would  reply  as  likewise  stated  below\  For  conveni- 
ence we  may  refer  to  the  former  advocate  as  M.  W.  (Me- 
teoric Waters)  and  to  the  latter  as  I.  R.  (Igneous  Rocks). 

-48- 


M.  W.  would  state  at  the  start  that  meteoric  waters  are  JAS.  F.  KEMP. 
the  only  waters  entering  into  the  crust  of  the  earth  or 
emerging  from  it,  which  cut  any  figure  in  the  economy 
of  Nature.  Upon  this  sweeping,  axiomatic  principle  his 
case  would  be  especially  based.  But  I.  R.  replies  that 
abundant  experience  indicates  that  hot-springs  are  asso- 
ciated with  expiring  vulcanism,  are  particularly  large  in 
arid  regions,  are  known  in  several  cases  to  yield  more  wa- 
ter than  the  capacity  of  the  catchment  basin  tributary  to 
them,  and  are  therefore  fed  by  the  emissions  of  cooling 
eruptive  rocks,  which,  as  we  know  from  volcanoes,  con- 
tain vast  supplies  of  the  elements  of  water.  He  would 
add  that  hot-springs  have  without  much  doubt  been  the 
great  agents  in  the  primary  deposition  of  ores  and  gangue 
minerals  in  veins. 

M.  W.  would  next  postulate  that  gravity  is  the  prime 
mover  in  the  underground  circulations  of  the  meteoric 
waters,  and  that  it  is  reinforced  by  the  expansion  of  the 
waters  from  the  increase  in  temperature  with  depth.  The 
descending  cold  and  heavy  column  forces  up  again  the  as- 
cending heated  and  expanded  column.  I.  R.  replies  that  in 
the  restricted  areas  of  vulcanism,  the  energy  afforded  by 
highly  heated  bodies  of  igneous  rock  is  vastly  superior  to 
gravity,  above  all  as  an  expelling  agent  and  especially 
through  the  production  of  steam.  If,  moreover,  adds  I. 
R.,  we  calculate  on  the  best  experimental  data,  the  head 
that  would  be  produced  by  the  hea\  ier  descending  column 
of  colder  water  to  a  depth  of  10,000  feet,  as  against  the 
ascending  heated  column,  it  is  insignificant,  and  except  so 
far  as  the  water  enters  at  a  greater  elevation  than  its  point 
of  emergence,  gravity  as  a  prime  mover  practically  dis- 
appears. 

M.  W.  would  emphasize  the  universal  presence  of  the 
meteoric  waters,  and  of  the  normal  increase  in  temperature 
with  descent  into  the  earth.  Somewhat  in  the  spirit  of 
the  Uniformitarian  School  of  Geologists,  he  would  urge 
the  incomparable  claims  to  confidence  of  the  small,  slow 
but  widespread  causes  in  the  production  of  results.  To 
which  I.  R.  would  reply  that  veins  and,  above  all,  veins 
rich  enough  in  metallic  minerals  for  profitable  exploitation 


—  49  — 


JAS.  F.  KEMP,  are  the  exception  and  are  extremely  rare,  and  that  for 
this  very  reason  they  must  have  been  produced  by  some 
local  and  exceptional  cause.  Whereas  we  find,  as  a  mat- 
ter of  experience,  no  such  widespread  vein  formation  as 
would  be  implied  by  JM.  W. 

M.  W.  would  lay  great  emphasis  upon  the  cavities,  large 
and  small,  in  rocks,  would  plot  curves  to  show  the  wide 
area  drawn  upon  by  an  uptake,  natural  or  artificial,  and 
would  show  that  the  deeper  the  uptake,  the  wider  the 
tributary  area,  until  depths  were  reached  at  which  cavities 
become  physical  impossibilities,  that  is,  at  a  maximum 
of  30,000  feet  for  resistant  rocks.  I.  R.  replies  that  actual 
experience  in  those  mines  which  have  reached  consider- 
able depths,  say  over  2,000  feet,  and  sometimes  less,  goes 
to  show  that  the  water,  if  impounded  in  the  levels  above, 
diminishes  with  depth,  and  that  the  lower  workings  are  in 
positively  dry  rock  and  may  be  dusty,  even  in  regions  of 
heavy  rainfall,  and  of  synclinal  structure.  The  few  deep 
and  wet  mines  are  in  regions  of  expiring  vulcanism. 

M.  W.  realizing  from  this  that  the  very  foundations  of 
his  elaborate  argument  are  crumbling  in  ruins,  hastens 
to  "hedge"  by  stating  that  at  the  time  of  vein-formation 
and  for  its  limited  duration,  the  rocks  were  open  and  per- 
meable, but  that  the  deposition  of  mineral  matter  or 
"cementation"  has  plugged  them  and  cut  off  the  former 
supplies  of  water.  I.  R.  then  remarks  the  enormous  re- 
striction which  this  imposes  upon  the  sweeping  statements 
of  the  earlier  presentation  by  M.  W. ;  expresses  his  sur- 
prise that,  even  granting  cementation,  more  water  is  not 
found,  and  insists  that  none  the  less  the  down-takes,  in 
which,  not  cementation  but  solution  prevails,  ought  to  con- 
tinue to  afford  water  to  the  excavations.  He  insists  that 
in  the  large  way  the  permeability  of  rocks  has  been  over- 
rated, and  he  therefore  falls  back  on  the  greater  claims  of 
igneous  intrusions  to  confidence  as  primary  causes.  He 
contends  that  when  the  emissions  and  energy  contributed 
by  them  ceased  with  their  refrigeration  vein-formation 
and  water  supply  likewise  ceased. 

M.  W.  emphasizes  the  tremendous  complexity  of  the 
problem;  the    difficulty    of   tracing  waters  to  their  real 

—  50  — 


source;  their  deep  vertical  descents,  their  wide  lateral  JAS.  F.  KEMP. 
wanderings,  and  their  uprisings  from  the  profound  depths. 
He  urges  the  need  of  criteria  for  whose  even  partial 
statements  he  looks  to  the  publications  of  the  future,  and 
to  whose  complete  collection  many  years  of  labor  must 
be  devoted.  I.  R.  replies  that  if  one  starts  with  an  as- 
sumption of  agents  and  methods  of  precipitation,  which 
can  be  applied  to  the  cases  in  hand  only  with  great  diffi- 
culty, the  complexity  becomes  something  awful,  just  as  the 
Ptolemaic  astronomers  were  driven  to  endless  cycles  and 
epicycles  in  trying  to  explain  on  faulty  assumptions,  what 
the  Copernican  system  rendered  comparatively  simple  and 
intelligible.  He  urges  that  the  advocates  of  the  influence 
of  the  igneous  rocks  are  doing  for  that  branch  of  geology 
which  relates  to  ore-deposits  what  Copernicus  did  for  as- 
tronomy— and  that  is,  they  are  bringing  into  the  field 
agents  which  are  comparatively  simple  and  incomparably 
efficient. 

There  are  other  considerations  regarding  ore-deposits 
which  are  of  importance  and  of  interest,  but  which  do  not 
involve  differences  of  opinion  upon  theoretical  points. 
They  need  to  be  understood  by  the  miner,  but  they  are 
not  fundamental;  for  example,  the  enrichment  of  veins 
near  the  water  level  or  for  short  distances  below  it,  by 
the  leaching  of  the  upper  portions  in  the  descent  of  the 
surface  waters.  Certain  peculiar  mineral  aggregates  are 
characteristic  of  these  enrichments,  such  as  chalcocite  and 
the  distinctive  silver  minerals,  but  it  is  also  true  that  the 
richest  ore  in  mines  may  lie  3,000-3,500  ft.  down  the  slope 
or  shaft,  as  at  Przibram  and  Grass  Valley.  Nevertheless, 
geologists  are  under  great  obligations,  more  especially  to 
Mr.  Weed,  for  emphasizing  these  relations. 

It  must  not  be  forgotten  that  in  regions  physiographic- 
ally  old,  we  have  left  only  the  stumps  of  veins  which 
may  have  once  extended  considerably  higher.  At  the 
same  time,  in  connection  with  matters  of  genesis,  the  root 
IS  more  important  than  the  trunk  and  limbs. 

In  general,  the  more  sound  geology  that  can  be  worked 
into  systems  of  classification  and  into  terminology,  the 
more  helpful  they  will  be  to  engineer  and  geologist.    The 


—  51  — 


,  JAS.  F.  KEMP,  closer  we  keep  in  touch  with  the  miner  and  with  the  hard 
facts  of  his  experience  the  more  justification  for  the  exist- 
ence of  geology.  There  is  no  geologist  who  may  not  profit 
by  the  experience  of  an  observant  and  grizzled  veteran 
of  the  pick  and  drill. 

P.  L.  RANSOME.  Mr.  Ransome  was  the  next  speaker.    He  said : 

In  a  recent  paper  on  ore-deposits,  Prof.  Vogt  has  re- 
marked that  "the  precise  tracing  of  the  boundary  between 
eruptive  after-action  and  the  work  of  the  underground 
waters,  is  a  labor  for  the  future."  It  is  a  question 
whether  the  genetic  classification  proposed  at  a  recent 
meeting  by  Mr.  Weed  has  in  any  way  curtailed  this  field 
of  future  investigation.  That  the  time  is  hardly  ripe  for 
a  satisfactory  genetic  classification  of  ore-bodies  is  shown 
not  only  by  the  widely  divergent  views  held  by  eminent 
students  of  the  subject,  but  by  the  trend  of  the  present 
discussion  which  insistently  transgresses  its  implied  lim- 
its, to  concern  itself  A/ith  the  underlying  processes  of  ore- 
deposition,  rather  than  with  the  grouping  of  accepted 
types  of  known  origin. 

I  shall  try  to  point  out  briefly  what  seem  to  me  to 
be  some  objections  to  the  plan  of  classification  adopted  by 
Mr.  Weed  and  to  illustrate  these  objections  by  reference 
to  ore-deposits  with  which  I  am  familiar. 

The  use  of  the  critical  temperature  as  a  criterion  of 
classification  gives  to  the  scheme  an  attractive  appear- 
ance of  precision,  which,  however,  is  more  apparent  than 
real.  For  it  implies  that  contact  metamorphism  ceases 
and  entirely  different  processes  come  into  play  the  mo- 
ment the  magma  cools  below  the  temperature  of  365**  C. 
As  a  matter  of  fact,  however,  water  (which  is  admittedly 
the  chief  agent  concerned  in  mineralization)  will  still 
exist  as  a  vapor  below  the  critical  temperature,  provided 
the  pressure  be  not  excessive,  and  it  is  yet  to  be  proved 
that  substances  given  off  from  the  magma  above  their 
critical  temperatures  are  the  only  agencies  capable  of  pro- 
ducing the  minerals  characteristic  of  contact  zones. 
I  While  it  is  admitted  that  molten  magmas  contain  vari- 
ous substances  that  may  be  given  off  in  the  state  of  gas 

—  12  — 


or  vapor  when  the  magma  is  erupted  near  the  surface,  it  F.  L.  RANSOME, 
is  a  debatable  question  whether  the  magma  is  so  satu- 
rated with  these  substances  as  to  give  them  off  in  abund- 
ance under  great  pressure,  and  above  the  critical  temper- 
ature. The  fact  that  granite  when  heated  to  i,ooo°  C. 
was  found  by  Gautier  to  give  off  more  than  loo  times  its 
own  volume  of  gases  and  vapors  shows  that  under  the 
conditions  of  original  solidification  these  gases  were  re- 
tained in  the  rock. 

Part  of  the  argument  in  favor  of  a  pneumatolytic 
origin  for  certain  ore-deposits  is  drawn  from  the  well- 
known  effect  of  mineralizing  agents  in  the  artificial  pro- 
duction of  minerals  by  synthesis.  The  mineralizing 
agent  in  most  cases,  however,  either  does  not  enter  into 
the  composition  of  the  mineral  formed,  or  does  so  in 
very  small  amounts.  An  ore-body,  on  the  other  hand, 
implies  a  local  concentration  of  materials  elsewhere  very 
sparingly  present  in  the  rocks.  It  cannot  be  explained 
as  the  result  of  crystallization  of  material  already  pro- 
vided, in  the  presence  of  some  mineralizing  agent  given 
off  from  a  contiguous  body  of  molten  magma.  It  im- 
plies extensive  transfers  of  material,  and  it  is  this  con- 
siderable concentration  and  transfer  which  I  find  most 
difficult  to  ascribe  entirely  to  pneumatolytic  processes, 
particularly  when  it  is  remembered  that  one  of  the  char- 
acteristics of  ordinary  contact  metamorphism  is  a  sur- 
prisingly slight  change  in  the  chemical  composition  of 
the  metamorphosed  rock.  The  case  of  the  garnetized 
limestone  of  San  Jose  in  Mexico,  cited  in  a  recent  paper 
by  Prof.  Kemp,  is  not  clearly  an  exception  to  this  state- 
ment. His  argument  for  the  original  purity  of  the  lime- 
stone, and  the  consequent  introduction  of  material  to 
form  the  garnet,  is  based  upon  smelter  records.  But  it 
is  not  unusual  to  find  that  the  metamorphism  of  an  impure 
limestone  is  a  clarifying  process,  resulting  in  the  forma- 
tion of  garnet  and  pure  crystalline  calcite.  Moreover, 
smelters  as  a  rule  seek  the  purest  limestone  for  fluxing 
purposes.  At  Cananea,  for  example,  where  extensive 
garnetization  of  the  limestone  has  taken  place,  the  lime- 
stone for  smelting  purposes  is  brought  from  a  distance 

—  53  — 


F.  L.  RANSOME.  and  from  a  bed  that  cannot  be  taken  as  representing  the 
original  character  of  the  Hmestone  befot-e  metamorphism. 
,  The  entire  subject  of  pneumatolysis  is  one  of  great 
interest,  and  there  would  seem  to  be  here  a  field  for  ex- 
tensive experimental  work.  The  difficulties  in  the  way 
of  such  experiments,  involving  great  pressures,  high  tem- 
peratures and  time,  are  formidable,  but  perhaps  not  in- 
surmountable. It  is  one  of  many  lines  of  scientific  inves- 
tigation awaiting  the  happy  conjunction  of  the  right 
worker  and  an  available  fund. 

It  is  over  the  fourth  class  of  Mr.  Weed's  table — the 
gas-aqueous  or  pneum^to-hydato-genetic  deposits — that 
there  will  probably  be  most  difference  of  opinion.  One 
may  admit  the  action  of  pneumatolysis  in  the  formation 
of  some  contact  deposits  and  yet  hesitate  to  extend  the 
hypothesis  to  most  of  the  deposits  grouped  under  Class 
IV,  which  comprises  the  greater  number  of  workable 
metalliferous  ore-bodies.  It  is  generally  admitted  that 
water  has  been  the  vehicle  by  which  these  ores  have  been 
deposited.  So  much  may  fairly  be  deduced  from  the 
observable  facts.  The  question  whether  this  water  is 
mainly  meteoric  or  has  been  expelled  from  solidifying 
masses  of  eruptive  rock  approaches,  at  present,  the 
ground  of  speculation,  and  with  the  hypothesis  that  gases 
given  off  from  igneous  rocks  are  directly  mingled  with 
the  ore-depositing  solutions,  that  ground  is  fairly  en- 
tered. My  own  limited  experience  has  rather  inclined 
me  to  the  view  that  most  of  the  ore-bodies  grouped  under 
Class  IV  have  been  formed  after  the  solidification  of  the 
eruptive  rocks  with  which  they  are  more  or  less  closely 
associated,  and  that  the  principal  agent  in  their  concen- 
tration and  deposition  has  been  meteoric  water. 

In  the  Sierra  Nevada  of  California,  in  what  is  known 
as  the  Mother  Lode  District,  the  gold  quartz  veins  be- 
long to  the  sericitic-calcitic  class  as  defined  by  Lindgren, 
and  are  Cretaceous  in  age.  The  great  eruptions  of  grano- 
diorite  also  belong  to  this  same  period.  But  the  veins 
are  distinctly  later  than  the  granodiorite,  and  in  many 
cases  occupy  fissures  in  the  latter  rock.  The  granodiorite 
had  therefore  solidified  before  the  ores  were  deposited. 


—  54  — 


and  any  direct  participation  of  pneumatolytic  processes      F.  L.  RANSOME. 
is  barred  out  as  far  as  known  intrusive  masses  are  con- 
cerned. 

The  San  Juan  region  in  Colorado  has  been  frequently 
cited  in  illustration  of  vein-relationships,  which,  as  far 
as  that  region  is  concerned,  are  entirely  imaginary.  Thus 
the  authors  of  two  recent  papers  discussing  the  relation 
between  ore-deposition  and  igneous  activity,  have  referred 
to  the  region  as  containing  three  distinct  sets  of  veins, 
each  set  characterized  by  ores  of  different  mineralogical 
character.  As  I  have  elsewhere  shown,  this  distinction 
has  no  basis  in  fact,  and  is  a  case  of  hasty  generalization 
from  very  incomplete  data.  The  lodes  of  the  Silverton 
quadrangle,  in  this  region,  which  are  generally  associated 
with  propylitic  alteration  of  the  country  rock,  are  not  only 
later  than  the  great  series  of  volcanic  lavas  and  tuffs, 
but  are  later  than  the  monzonitic  intrusions  that  invade 
the  volcanics.  Many  of  the  lodes  occur  in  fissures  which 
cut  the  monzonites  and  the  mineralization  took  place 
subsequently  to  the  solidification  of  all  the  eruptive  rocks 
known  in  the  region. 

In  the  Rico  Mountains,  Colorado,  there  are  some  de- 
posits in  Devonian  limestone,  which  consist  of  pyrite, 
chalcopyrite,  sphalerite,  galena  and  specularite,  associated 
with  garnet,  wollastonite,  chlorite  and  pyroxene.  These, 
although  not  now  observably  in  contact  with  intrusive 
rock,  are  probably  to  be  classed  as  true  contact  deposits, 
and  are  possibly,  in  part,  of  pneumatolytic  origin.  But 
the  lode  and  blanket  deposits  of  this  district  are  distinctly 
later  in  age  than  the  intrusive  masses  of  porphyry,  and 
were  formed  after  the  solidification  of  the  latter.  The 
porphyry  itself  is  often  extensively  mineralized. 

The  copper  deposits  at  Globe,  Ariz.,  originally  pyrite 
and  chalcopyrite,  were  deposited  after  extensive  intru- 
sions of  olivine  diabase.  The  ore  occurs  chiefly  in  lime- 
stone, quartzite  and  in  the  diabase  itself.  The  ores  in 
the  diabase  have  the  form  of  veins  or  lodes,  and  were 
evidently  formed  after  the  diabase  had  solidified  and 
had  been  greatly  faulted. 

In   the    Bisbee   District,   Arizona,    the   principal    ore- 

—  55  — 


F.  L.  RANSOME.  bodies  occur  as  replacements  in  limestone  adjacent  to 
an  intrusive  mass  of  granite  porphyry,  and  related  also 
to  faults  cutting  the  limestones  and  older  rocks.  The 
original  ores,  from  which  the  workable  bodies  have  been 
iormed  by  oxidation  and  by  sulphide  enrichment,  consist 
of  pyrite  and  chalcopyrite.  They  occur  chiefly  in  the 
limestone,  but  the  entire  mass  of  porphyry  is  altered  and 
abundantly  impregnated  with  pyrite,  sometimes  accom- 
panied by  chalcopyrite.  Here  again  the  mineralization  is 
apparently  later  than  the  solidification  of  the  only  known 
eruptive  rock  to  which  it  bears  any  relation. 

In  conclusion,  I  do  not  wish  to  deny  that  pneuma- 
tolysis  may  be  an  effective  factor  in  ore-deposition,  but 
there  seems  to  be  a  tendency  to  carry  this  attractive  and 
suggestive  hypothesis  a  little  further  than  the  facts  war- 
rant. The  few  mining  districts  that  I  have  studied  have 
led  me  to  regard  the  action  of  meteoric  waters,  usually 
heated  and  rendered  physically  and  chemically  active 
by  masses  of  intrusive  rock,  as  more  important  and  more 
far-reaching  than  indicated  in  the  proposed  genetic 
scheme  of  Mr.  Weed,  which  has  provoked  the  present  dis- 
cussion. 

Mr.  Hayes  then  introduced  Mr.  T.  A.  Rickard,  who 
had  been  invited  by  the  society  to  attend  the  meeting  in 
order  to  take  part  in  the  discussion.     Mr.  Rickard  said: 

T.   A.  RICKARD.  It  is  evident  that  as  yet  there  is  no  unanimity  concern- 

ing the  origin  of  ores,  and  until  a  certain  degree  of  har- 
mony of  ideas  has  been  attained  no  system  of  classification 
is  likely  to  be  generally  accepted ;  nevertheless  the  classi- 
fications submitted  by  Messrs.  Weed  and  Spurr  have 
served  a  most  useful  purpose  in  crystallizing  their  own 
views  on  genetic  principles,  and  in  affording  a  clear  field 
for  discussion  on  the  part  of  those  who  hold  different  opin- 
ions. "All  knowledge,"  says  Locke,  "consists  in  seeing 
likeness  and  difference."  That  defines  classification;  by 
means  of  it  we  shall  be  able  to  analyze  existing  concep- 
tions of  the  process  of  ore  formation,  so  as  to  separate  the 
points  upon  which  we  agree,  from  those  which  we  dispute 

—  56- 


and  from  the  much  larger  array  of  facts  concerning  which 
no  one  possesses  precise  knowledge. 

The  discussion  has  emphasized  the  divergence  of  views 
between  acknowledged  authorities.  Formerly,  when  min- 
ing did  not  know  geology,  both  suffered  thereby;  when 
geology  was  an  arrogant  youngster  and  mining  only  a 
blind  digger,  it  was  fashionable  to  impute  to  vague  igneous 
agencies  and  unknown  gaseous  emanations  the  responsibil- 
ity for  the  occurrence  of  ores.  To  this  period,  which 
lasted  long,  a  sort  of  "dark  ages"  in  the  history  of  mining 
geology,  there  succeeded  a  recognition  of  the  effects  of 
water  in  depositing  minerals  within  the  earth  fractures. 
Posepny's  monograph  represents  the  culmination  of  this 
philosophy,  for  when  Prof.  Van  Hise  elaborated  his  de- 
ductions from  physical  laws,  the  tide  of  opinion  had  al- 
ready begun  to  turn  by  reason  of  the  researches  of  Vogt. 
Kemp,  Spurr  and  Weed  have  driven  home  Vogt's  con- 
clusions, and  by  observation  and  discussion  they  have  ad- 
vanced the  theory  of  igneous  agencies  until  the  aqueous 
factor  is  almost  driven  to  the  surface.  Van  Hise  claimed 
for  his  domain  a  depth  which  reached  at  least  six  miles 
into  the  interior  of  the  earth,  now  the  advocates  of  mag- 
matic  differentiation  propose  to  confine  the  agency  of  free 
water  to  a  shallow  strip  somewhere  near  the  surface.  The 
theory  of  an  aqueous  deposition  of  ores  is  thus  threatened 
by  an  igneous  intrusion  of  a  very  violent  kind. 

The  agency  of  water  was  at  one  time  underestimated ; 
that  of  magmatic  differentiation  was  not  recognized  until 
lately; and  as  each  branch  of  the  subject  had  been  elabo- 
rated, the  enthusiasm  of  its  advocates  has  carried  them 
beyond  bounds.  The  swing  of  the  pendulum  just  now  is 
on  the  igneous  side,  by  and  by  the  pendulum  will  slowly 
fall  back  to  a  compromise  of  views,  so  that  with  each 
elaboration  of  this  many-sided  problem  we  shall  gradually 
attain  to  a  more  comprehensive  theory,  capable  at  length 
of  covering  the  multitudinous  ways  in  which  ores  are 
found  in  nature. 

The  classifications  proposed  by  Messrs.  Weed  and  Spurr 
are  extremely  suggestive.  To  a  large  extent  they  are  sup- 
ported by  the  broad  fact  of  an  intimate  connection  be- 


T.  A. 


—  57  — 


T.  A-  RICKARD.  tween  ore-deposits  and  igneous  rocks.  The  miner*s  fond- 
ness for  an  environment  of  "porphyry"  may  not  be  well 
reasoned,  but  it  is  the  result  of  wide  experience.  It  ex- 
presses a  general  phenomenon.  A  phenomenon  is  a  thing 
you  do  not  understand. 

During  the  past  three  years  I  have  been  collecting  data 
upon  the  geological  distribution  of  the  precious  metals  in 
Colorado.  It  is  a  remarkable  fact  that  in  this  single  mining 
region  the  profitable  mines,  exploiting  gold  and  silver 
ores,  occur  within  every  geological  terrain  from  the  Ar- 
chean  granite  to  a  Tertiary  conglomerate ;  at  this  moment 
mining  is  going  on  in  terrains  belonging  to  all  the  prin- 
cipal subdivisions  of  geological  time  and  amid  a  variety 
of  petrographic  environment  which  includes  nearly  all  of 
the  principal  sedimentary  and  crystalline  rocks.  In  ar- 
riving at  the  age  of  the  country  enclosing  these  lodes  it 
has  frequently  been  difficult  to  consider  the  sedimentary 
apart  from  the  intrusive  igneous  rock,  and  it  is  not  too 
much  to  say  that  there  is  not  a  mining  district,  among  the 
sixty-five  which  I  have  tabulated,  in  which  igneous  rocks 
do  not  occur  in  close  association  with  the  ore-deposits. 
Moreover,  out  of  six  hundred  representative  mines  there 
are  at  least  two  hundred  which  have  yielded  ore  from  sedi- 
mentary rocks  belonging  to  more  than  one  geological 
period.  Thus,  any  generalizations  based  upon  the  age  or 
the  composition  of  the  country  rock  are  completely  shat- 
tered. This  serves  but  the  more  to  emphasize  the  fact, 
which  is  too  general  to  be  a  coincidence,  that  the  valuable 
ore-deposits  are  connected  with  the  occurrence,  in  the 
vicinity,  of  intrusive  igneous  rock.  I  have  been  led  to 
conclude  that  the  deposition  of  ore  represents  the  results 
of  that  thermal  activity  which  is,  as  it  were,  the  dying 
breath  of  volcanic  activity,  and  that  the  dikes,  sheets,  cores 
and  laccoliths  were  factors  in  stimulating  the  circulation 
of  mineral  solutions.  Not  that  the  igneous  rock  was  the 
direct  ore-carrier,  but  that  it  energized  the  chemical  work 
of  the  solutions,  and  that  it  opened  a  subsequent  passage- 
way for  such  solutions,  whereby  they  reached  the  locus  of 
their  deposit.  As  Mr.  Emmons  has  observed  already,  it 
is  likely  that  the  igneous  matter  brought  the  metals  within 

-58  — 


the  region  of  water  circulation,  and  that  the  actual  con-     T.  A. 
centration  of  ore  which  is  exploited  by  man  to-day  was  the 
result  of  the  subsequent  activity  of  the  underground  water 
system. 

The  dryness  of  deep  mines  and  its  bearing  upon  the  gen- 
eral conception  of  the  underground  circulation  has  been 
emphasized  by  Prof.  Kemp  in  a  recent  very  suggestive 
paper.  It  is  a  question  on  which  I  have  been  collecting 
data  for  the  past  two  years,  for  it  is  fundamental  to  any 
comprehensive  theory  of  ore-formation.  This  brings  me 
to  a  view  of  the  subject  which  I  have  previously  suggested.  - 
In  discussing  Posepny's  paper  in  1893,  I  used  the  simile  of 
a  domestic  hot  water  system.  Prof.  Le  Conte  and  Mr. 
Emmons  have  at  various  times  referred  to  this  analogy, 
as  I  used  it,  and  I  am  therefore  encouraged  to  apply  it  in 
a  more  comprehensive  manner.  Data  afforded  by  mine 
workings  indicate  that  a  condition  of  rock-saturation  does 
not  persist  indefinitely  downward,  but  that  there  is  a  wa- 
ter zone,  extending  from  the  ground-water  level  for  a 
further  depth  of  several  hundred  feet.  Below  that  horizon, 
which  has  limits  varying  with  locality,  whatever  free  wa- 
ter does  exist  is  confined  to  definite  channels,  that  is,  vein- 
fractures  similar  to  those  in  which  we  find  the  ore  to-day. 
In  depth  we  encounter  vulcanism.  Thus  we  have  the 
elements  of  a  circulatory  system ;  heat  at  the  base,  a  series 
of  channels  leading  to  surface  and  a  reservoir  of  cold  wa- 
ter at  the  top.  It  is  not  likely  that  gravitation  is  the  main 
agent  in  giving  movement  to  the  underground  waters; 
the  decrease  in  density  due  to  rising  temperature  must  be 
offset  against  the  friction  of  the  rock  walls,  and  it  is  prob-  • 
able  that  superheated  water-vapor  serves  as  the  main 
propeling  force,  as  is  suggested  by  the  testimony  of  vol- 
canic action.  Nor  is  it  likely  that  the  water  is  wholly  of 
meteoric  origin.  Much  of  it,  like  other  factors  in  vein 
formation  is  indirectly  traceable  to  the  sources  of  eruptive 
activity.  Nor,  again,  must  the  simile  of  the  hot-water 
system  be  taken  too  literally.  Underground  waters  do  not 
travel  along  pipes,  but  along  fractures  and  those  systems 
of  fracture  which  are  called  sheer  zones,  affording  no 
continuous  free  passage,  but  a  path  of  circulation  which 

—  59  — 


T.  A.  RICKARD.  is  sought  out  with  difficulty  and  followed  with  that  pa- 
tience which  "hardens  the  ruby  in  a  million  years."  The 
geologist  has  a  large  account  at  the  bank  of  Time  and 
is  entitled  to  draw  upon  it. 

The  deepest  metal  mines,  in  the  Lake  Superior  region, 
are  dry  at  the  bottom ;  the  deepest  coal  mines  in  Germany 
and  England  exhibit  the  maximum  of  dust;  the  deepest 
gold  mine  in  the  world  does  not  need  to  use  a  pump ;  many 
mines  in  the  dry  regions  of  Australia  are  unhealthily  dusty 
at  a  shallow  depth;  in  the  Transvaal,  miner's  phthisis 
is  brought  on  by  excessive  dust  in  the  air  of  the  workings, 
— these  facts  speak  for  themselves.  It  is  useless  to  speak 
of  an  indefinite  water  saturation  in  the  face  of  them.  More- 
over, the  heavy  inflow  of  water  in  mines  coincides  usually 
with  a  comparatively  shallow  zone,  the  bodies  of  water 
encountered  underground  are  eventually  pumped  out ;  so 
that  there  is  plenty  of  evidence  which  is  quite  opposed  to 
the  conception  of  a  water-soaked  region  of  indefinite  ver- 
tical extent.  It  is  a  matter  which  is  wortny  of  consider- 
ation, because  it  affects  the  ideas  which  we  form  concern- 
ing the  precipitation  of  ore  from  solutions  in  their  ap- 
proach to  the  surface.* 

C.  R.  VAN  HISE.  The  discussion  was  continued  by  Prof.  C.  R.  Van  Hise. 
He  believed  that  in  order  to  get  a  proper  perspective  and 
to  appreciate  differences  of  view,  it  would  be  well  to  first 
give  a  summary  of  points  of  agreement.  Attention  was 
called  by  the  speaker  to  the  fact  that  in  his  paper,  pub- 
lished two  years  ago  under  the  title  of  "Some  Principles 
Controlling  the  Deposition  of  Ores,"  he  had  stated  that 
the  metals  of  some  ores  are  directly  derived  from  recent 
adjacent  igneous  rocks;  that  the  ultimate  source  of  all  the 
metals  of  ore-deposits  is  the  igneous  rocks;  that  igneous 
rocks  have  an  influence  upon  ore-deposits  by  contributing 
metals  to  them  and  by  contributing  solutions;  they  also 
produce  important  effects  by  heating  solutions  of  meteoric 
origin  and  in  forming  the  openings  which  may  be  fol- 
lowed by  such  solutions. 


^This  idea  was  subsequently  set  forth  at  greater  length,  under  the  titlfr 
of  "Water  in  Veins.  A  Theory,"  in  the  Engineering  and  Mining  Jour- 
KAi,  of  March   14th,   1903. 

—  60  — 


As   a   basis   for   discussion   the   following  provisional      C.  R.  VAI^  HISS. 

generic   classification  of   metallic   ore-deposits   was   sub- 
mitted : 


Metallic 

Ore 
Deposits, 


'  Sedimentary. 


Igneous. 


Metamorphic. 


f  (a)  Chemical 
I  precipitates. 


(b)  Mechanical 
concentrates. 


(a)  Magmatic 
segregations. 

"(a)  Deposited 
from  gaseous 
solution. 


(b)  Deposited 
from  aqueous 
solution. 


f  (i)  Residuary 
deposits. 

J  (2)  Stream 
\  deposits. 

(3)  Beach 
I  deposits. 


(1)  Ascending 
waters. 

(2)  Descending 
waters. 

(3)  Ascending 
and  descending 

^waters. 


Referring  to  the  most  recent  classifications  of  ore-de- 
posits, the  placing  of  a  large  proportion  of  ore-deposits 
as  of  pneumatolytic,  fumarolic,  solfataric,  and  pneumato- 
hydato-genetic  origin,  was  deprecated.  The  question  was 
asked  as  to  the  criteria  by  which  ore-deposits  are  known 
to  be  deposited  by  gaseous  solutions. 

The  criterion  which  seemed  to  be  of  most  weight  to  the 
speaker  was  the  formation  simultaneously  with  the  ores 
of  such  heavy  anhydrous  minerals  as  garnet,  pyroxene, 
wollastonite,  tourmaline  and  biotite.  For  those  ores 
which  are  deposited  simultaneously  with  these  minerals  it 
is  believed  that  they  are  deposited  under  the  conditions 
of  the  deep-seated  zone  of  rock  flowage,  and  probably  at 
temperatures  above  the  critical  temperature  of  water.  It 
is  further  to  be  suggested  that  the  frequent  lack  of 
definite  boundaries  for  these  ores  and  their  dispersed  dis- 
tribution through  rocks  have  a  similar  bearing. 

If  the  question  cannot  yet  be  fully  answered  as  to  the 
criteria  by  which  ores  deposited  by  gaseous  solutions  are 
to  be  recognized,  what  shall  be  said  as  to  the  criteria  by 
which  such  ores  are  divided  into  sub-classes?  The  plac- 
ing of  the  various  ore-deposits  of  many  well-known  dis- 
tricts in  such  classes  as  fumarolic,  solfataric,  pneuma- 


C.  R.  VAN  HISE.  tolytic,  etc.,  without  giving  the  evidence  for  such  distribu- 
tion, seemed  to  the  speaker  to  be  premature. 

The  criteria  by  which  ores  deposited  by  aqueous  solu- 
tions may  be  discriminated  were  briefly  summarized.  The 
more  important  ones  were  held  to  be  the  following: 

First. — The  material  which  has  filled  the  numerous 
openings  of  great  sandstone,  conglomerate,  amygdaloid 
and  tuff  formations,  thus  cementing  them,  is  agreed 
by  all  to  have  been  deposited  by  aqueous  solutions.  The 
evidence  seems  to  be  conclusive  that  the  simultaneous  fill- 
ing of  joint  and  fissure  openings  and  the  replacement  of 
rocks  by  minerals  like  those  of  the  cementation  materials, 
are  also  the  work  of  aqueous  solutions.  But  here  and 
there  the  fillings  of  various  kinds  carry  a  minute  fraction 
of  a  per  cent,  of  gold  and  silver,  or  a  small  per  cent, 
of  copper,  lead  or  zinc,  and  are  consequently  ores.  Such 
ores  are  almost  certainly  deposits  from  aqueous  solutions. 

Second. — The  dominant  gangue  minerals  which  are  de- 
posited simultaneously  with  the  great  majority  of  ores, 
both  in  openings  and  in  the  wall  rocks,  are  the  hydrous 
silicates,  such  as  the  zeolites,  the  kaolinites,  sericite  and 
chlorite;  the  carbonates,  such  as  calcite,  dolomite  and 
siderite ;  the  oxides,  such  as  quartz  and  hematite.  These 
minerals  are  the  same  as  those  that  do  the  general  work 
of  cementation.  Moreover,  they  are  the  minerals  which 
have  been  observed  to  be  deposited  by  aqueous  solutions 
at  Steamboat  Springs,  Sulphur  Bank,  Boulder  Hot 
Springs,  Yellowstone  Hot  Springs  and  other  localities. 
At  some  of  these  localities,  notably  at  Steamboat  Springs, 
Sulphur  Bank  and  Boulder  Hot  Springs  (described  by 
Weed),  small  quantities  of  ores  have  also  been  deposited. 
Therefore,  both  observation  of  the  actual  work  of  aqueous 
solutions  and  the  fact  that  the  minerals  formed  are  like 
those  which  have  done  the  general  work  of  cementation, 
lead  to  the  conclusion  that  ores  having  the  above-men- 
tioned gangue  minerals  as  associates,  are  the  deposits  of 
aaueous  solutions.  No  observations  have  been  made 
which  support  the  view  that  ores  having  such  gangue 
minerals  are  deposited  by  gaseous  solutions.  But  the 
J  ores  having  such  gangue  minerals  are  the  dominant  class, 

—  62  — 


and  it  follows  that  the  class  of  ores  deposited  by  aqueous  C.  R.  VAN  BldiSi 
solutions  is  of  greater  importance  than  any  other  class, 
and  probably  of  greater  importance  than  all  other  classes. 
Time  does  not  suffice  to  discuss  the  sedimentary  ores, 
nor  more  than  allude  to  the  igneous  ores.  In  reference 
to  the  latter,  it  is  well  known  that  the  corundum  ores  in 
certain  corundum  syenites  are  the  direct  products  of 
magmatic  segregation.  Also,  it  is  agreed  by  all  that  the 
titanic  iron  ores  are  produced  by  magmatic  segregation. 
These  ores,  although  large  in  total  mass,  are  often  low 
grade  and  are  at  present  of  little  or  no  economic  import- 
ance. The  important  point  in  this  connection  is  that 
aluminum  and  iron  are  the  two  most  abundant  metals 
of  nature.  The  fundamental  law  of  chemistry,  the  law 
of  mass  action,  is  here  applicable.  In  order  to  produce  a 
titanic  iron  ore  containing  60  per  cent,  metallic  iron 
from  a  rock  of  medium  basicity,  such  as  a  gabbro,  it  is 
necessary  to  suppose  only  that  the  iron  has  been  multi- 
plied seven  or  eight  times  beyond  the  original  amount 
in  the  rock.  It  is,  therefore,  easy  to  understand  why  the 
processes  of  magmatic  segregation  produce  such  materials 
as  titanic  iron  ore  and  aluminum  ores.  The  production  of 
ores  other  than  of  aluminum  and  iron  by  magmatic 
segregation  is  an  entirely  different  matter.  He  who  holds 
that  ores  of  nickel,  copper,  gold,  etc.,  are  produced  by 
magmatic  segregation  alone  should  determine  the  ratios 
between  the  amounts  of  these  elements  present  in  the 
original  rocks  and  in  the  ores.  When  these  ratios  are  de- 
termined one  will  be  able  to  see  whether  or  not  the  amount 
of  segregation  in  these  cases  is  comparable  with  that 
which  we  know  to  exist  in  the  cases  of  the  abundant 
elements  where  we  can  be  sure  of  the  nature  of  the  pro- 
cesses. 

The  discussion  was  concluded  by  Mr.  Weed,  who  said :      W.  H,  WEED. 

When  the  invitation  to  present  a  tentative  genetic  clas- 
sification of  ore-deposits  was  accepted,  the  scheme  was 
reduced  to  its  barest  outline,  and  then  sent  to  Mr.  Spurr, 
and  a  large  number  of  other  friends,  with  a  view  to  elicit- 
ing discussion.    As  a  means  of  provoking  discussion,  it 

—  63  — 


W.  H,  WEED,  has  been  eminently  successful,  and  it  has  drawn  out  two 
other  schemes  of  classification.  The 'fact  should  be  em- 
phasized, however,  that  my  genetic  classification  expressly 
disregards  commercial  considerations;  it  is  based  upon 
scientific  data,  and  is  intended  to  express  the  processes  of 
ore  formation.  There  may  be  but  one  example,  and  that 
of  little  economic  importance  in  a  class,  but  it  is  geneti- 
cally as  worthy  of  recognition  in  the  classification  as  the 
great  productive  deposits  mentioned  by  Van  Hise.  In 
presenting  this  scheme,  my  first  attempt  at  a  strictly  ge- 
netic grouping,  the  limitations  of  time  prevented  anything 
more  than  a  very  general  statement  of  the  principles  upon 
which  it  is  based.  In  the  table,  certain  ore-deposits  were 
mentioned  to  show  the  nature  of  the  deposits  meant  under 
certain  types.  Such  references  must  be  accepted  as 
tentative,  and  as  indicating  that  their  character  points  to 
the  origin  predicated,  to  be  confirmed  or  refuted  by  fur- 
ther study.  For  example,  magmatic  quartz  veins  have 
been  recognized  for  many  years.  If,  as  Beck  and  Spurr 
mamtain,  these  veins  are  sometimes  gold-bearing,  there 
should  be  a  place  for  them  in  the  classification.  Beck* 
says :  "The  aplite  dikes  carrying  the  gold  quartz  veinlets 
mmed  at  Berezovsk  in  the  Ural  Mountains,  are  genetically 
connected  with  the  granite  mass  of  Lake  Shartash. 
.  .  .  .  The  perfectly  fresh  stone-hewer's  chips  of  this 
granite,  which  is  there  quarried  for  stair  steps,  door  jambs, 
etc.,  are  creditably  stated  to  contain  as  much  as  one  grain 
of  gold  per  ton.  If  thus  the  intrusive  stock  proper  is 
auriferous,  it  need  not  be  wondered  at  that  the  subsequent 
outpourings  from  the  same  igneous  hearth  in  the  form  of 
aplites,  also  brought  with  them  a  gold  content  which  was 
concentrated  in  the  quartz  stringers.  These  quartz  string- 
ers have  to  be  considered  from  the  same  point  of  view  as 
regards  their  origin  as  the  pegmatites." 

Prof.  Van  Hise's  concluding  remarks  indicate  that  the 

author  of  the  proposed  classification  is  expected  to  present 

detailed  proof  that  each  subdivision  includes  deposits  of 

♦     the  origin  indicated.     This  seems  wholly  unreasonable; 

for  example,  the  igneous  origin  of  certain  copper  and 

•Richard  Beck,  "Lehre  von  Erzlagerstatten,"  p.  324- 
—  64  — 


nickel  deposits  is  maintained  by  Vogt,  who  has  presented  W.  H.  WEED. 
detailed  descriptions  of  the  deposits,  and  these  descriptions 
and  theory  have  been  accepted  by  numerous  geologists  of 
repute  and  quoted  in  text  books.  It  is  not  incumbent  upon 
the  author  of  a  classification,  confessedly  utilizing  the  work 
of  all  investigators,  to  present  detailed  proof  of  the  cor- 
rectness of  the  theories  of  well-known  men.  Adverse 
criticism  would  be  merited  were  such  work  ignored. 

As  regards  the  criticism  of  the  igneous  origin  of  copper 
and  nickel  ores,  the  fallacy  of  Prof.  Van  Hise's  argument 
lies  in  an  appeal  to  mass  action  while  disregarding  rela- 
tive solubilities.  Nor  is  it  evident  why  "differentiation" 
of  copper  and  nickel  is  a  very  different  matter  from  that 
of  differentiation  of  iron  ore.  The  mere  fact  that  there 
is  more  iron  in  a  rock  than  there  is  copper  does  not  of 
itself  and  in  disregard  of  solubility  constitute  a  valid 
reason  for  the  segregation  of  one  and  not  of  the  other. 
Chalcopyrite  and  pyrrhotite  are  well  known  to  be  primary 
constituents  of  certain  rocks,  and  the  pyroxenites  often 
carry  o.i  per  cent,  or  more  of  nickel  oxide ;  so  that  twenty 
times  this  amount  would  constitute  ore,  as  occurs  at  Web- 
ster, N.  C.  At  the  same  time,  it  is  recognized  that  there  is 
not  a  copper  deposit  of  demonstrated  igneous  origin  yet 
known  in  this  country. 

Concerning  the  deposits  made  by  igneous  emanations, 
whose  existence  is  so  grudgingly  admitted  by  two  of  my 
critics,  the  evidence  of  Aguilera,  Kemp  and  Lindgren  is 
rapidly  accumulating ;  and  it  is  confidently  believed  that, 
as  observers  become  better  acquainted  with  the  character 
of  these  deposits,  they  will  be  able  to  recognize  them,  and 
many  other  examples  will  be  found  in  this  country  and  in 
Mexico. 

"An  attractive  air  of  precision,"  to  quote  a  phrase  used 
in  the  recent  discussion,  is  given  to  a  citation  by  Mr. 
Ransome  of  the  well-known  California  gold  veins,  as 
proof  that,  because  the  veins  cut  the  granodiorite,  they 
must  of  necessity  have  no  connection  with  this  rock.  I 
need  only  mention  the  classic  tin-copper  veins  of  Cornwall 
and  Saxony,  as  well  known  examples  controverting  his 
contention.    It  is,  however,  well  known  to  petrographers 

-65- 


W.  H.  WEED,  that  there  is  frequently  a  close  gerxCtic  relation  between 
basic  and  siliceous  dikes  and  the  granite  rocks  cut  by  them. 
To  argue  that  veins  cutting  granitic  rocks  cannot  be  close- 
ly related  both  genetically  and  chronologically  to  them, 
is  as  unreasonable  as  to  assume  that  the  dikes  mentioned 
are  always  proof  of  a  distinct  period  of  igneous  activity. 

In  reply  to  Prof.  Van  Hise  it  appears  to  me  very  evident 
that  a  failure  to  recognize  criteria  perfectly  plain  to  other 
equally  competent  observers  is  not  a  proper  subject  for 
argument.  I  am  content  in  company  with  Geikie,  Fouque, 
Suess  and  Richard  Beck,  not  to  mention  those  who  have 
supported  me  in  this  discussion.  As  Prof.  Kemp  has  said, 
the  scene  shifters  fill  the  stage  in  the  "Principles  controll- 
ing the  deposition  of  ores."  It  is  Hamlet,  with  Hamlet 
left  out,  and  though  the  actors  appear  in  the  bill — ^the  lit- 
tle classification  presented  to-night — they  do  not  appear 
on  the  stage.  Admitting  as  he  does  to-night  that  igneous 
emanations  do  form  contact  metamorphic  ore-deposits,  it 
is  certainly  reasonable  to  believe  that  the  emanations 
could  and  do  mingle  with  ground-waters,  to  w^hich  they 
not  only  contribute  metallic  substances  to  be  deposited  as 
ores,  but  also  chlorine,  fluorine,  boric  acid,  etc.  These 
mineralizers  add  immensely  to  the  solvent  power  of  said 
waters  as  a  few  drops  of  hydrochloric  acid  will  sharpen 
the  water  in  which  calcite  is  dissolving,  and  such  hot 
waters  may  add  to  their  burden  of  precious  metals  by  at- 
tack upon  the  rocks  traversed.  To  quote  the  apt  words  of 
Suess :  "The  hot  waters  .  .  .  accordingly  cannot  be 
anything  else  than  the  consequence  of  the  degasification 
and  cooling  of  a  lava  mass  lying  not  far  below  the  surface ; 
emanations  which  are  too  feeble  to  cause  a  volcanic  erup- 
tion or  preparation  for  an  eruption.  It  may  be  imagined 
that  vadose  infiltrations  are  carried  up  by  the  less  hot 
springs,  that  i?,  that  in  descending,  meteoric  waters  will 
meet  hot  water,  which  prevents  further  penetration.  One 
may  even  imagine  that  in  the  course  of  an  oscillation  of 
the  internal  heat,  that  is  to  say,  in  case  of  diminished 
rise  of  heated  gases,  as  i.>  now  the  case  in  the  Yellowstone, 
the  vadose  water  is  enabled  to  penetrate  into  a  somewhat 
greater  depth,  and  with  a  renewed  rise  of  the  hot  gases 

—  66  — 


these  deeper  vadose  waters  may  even  be  taken  up  by  them     W.  H.  W££D. 

and  a  certain  mixture  ensue,  thus  vadose  additions  may 

cause  subordinate  features  masking  the  true  condition. 

But  the  essence  of  the  j^henomena,  just  as  in  the  case  of 

volcanoes,  consists  in  the  uprising  of  juvenile  (primitive) 

material,  the  'internal'  supply  or  contribution  from  the 

depth." 

It  is  true  that  the  views  now  held  are  slightly  at  vari- 
ance with  former  ones,  but  an  intimate  acquaintance  with 
and  study  of  the  hot  springs  of  the  Yellowstone  during  the 
past  twenty  years,  and  the  accumulation  of  facts  upon 
rainfall  and  flowage,  have  led  me  to  a  belief  in  the  state- 
ment just  given,  and  to  the  conclusions  of  Suess,  that  ore 
deposits  are  the  work  of  hot  springs,  and  that  hot  springs 
are  a  waning  phase  of  volcanic  activity.  It  is  hoped  at 
some  future  day  to  present  a  fuller  account  of  the  evidence 
for  this  classification.  It  has  fulfilled  its  mission  in  pro- 
voking discussion,  and  it  now  remains  for  us  all  to  gather 
new  facts  whose  study  will  either  prove  or  disprove  the 
correctness  of  the  classifications  which  have  been  pro- 
posed. 


—  67- 


OBSERVATIONS     ON    GOLD 
DEPOSITS* 

BY  CHESTER  WELLS  PURINGTON. 

This  distribution  of  ore  deposits  is  a  subject  which 
presents  to  the  mining  engineer  more  of  practical  im- 
portance than  does  the  discussion  of  the  origin  of  ores. 
While  not  decrying  the  usefulness  of  the  several  views 
which  are  now  the  focus  of  so  much  comment  among 
geologists,  I  would  urge  the  necessity  for  collecting  and 
publishing  more  data  concerning  the  distribution  of  ores, 
together  with  their  accompanying  phenomena.  In  the 
present  paper  the  purpose  is  to  treat  of  the  distribution 
and  rock  association  of  some  gold  deposits,  the  cases 
dealt  with  being  for  the  most  part  those  which  have 
come  under  my  personal  observation.  Although  it  is 
recognized  that  the  recording  of  such  observations  forms 
but  an  elementary  part  in  the  working  out  of  the  pro- 
found science  of  ore  deposits,  it  is  hoped  that  some  shreds 
of  value  may  be  found  among  these  notes  by  those  who 
shall  later  compile  lists  of  the  known  gold  occurrences. 

In  recent  years,  the  accurate  work  which  has  been  per- 
formed with  reference  to  the  testing  of  rock  and  rock 
areas,  remote  from  metalliferous  veins,  has  given  convinc- 
ing illustration  of  how  widespread  is  the  distribution  of 
gold.  Since  the  researches  of  Sandberger,  no  more  able 
work  has  been  done  in  the  line  of  determining  the  minute 
quantities  of  gold  and  silver  than  that  of  Mr.  Luther 
Wagoner,^  whose  results  have  recently  been  published. 
Mr.  Wagoner  has  shown  that  granite,  syenite,  basalt  and 


*This  carefully  prepared  contribution  to  the  discussion  on  ore  deposits 
was  published  in  The  Engineering  and  Mining  Journal  of  June  6,  13  and 
20,  1903.  It  is  proper  that  it  should  appear  as  a  part  of  the  present 
pamphlet. 

1  Luther  Wagoner,  "The  Detection  and  Estimation  of  Small  Quantities  of 
Gold  and  Silver."  Transactions  American  Institute  of  Mining  Engineers, 
190 1,  Vol.  XXXI,  p.  798. 


diabase,  of  the  igneous  rocks,  and  such  material  as  Car- 
rara marble  and  San  Francisco  Bay  mud,  representing 
sediments,  contain  gold  in  appreciable  quantities.  His 
specimens  were  selected  without  reference  to  the  distribu- 
tion of  metalliferous  provinces,  and  the  work  has  thus  a 
special  value.  It  is  possible  that  further  investigation 
along  the  line  of  these  experiments  may  show  that  the  dis- 
tribution of  gold  is  practically  universal. 

Mr.  T.  A.  Rickard,  in  one  of  his  recent  contributions" 
to  the  Transactions  of  the  American  Institute  of  Mining 
Engineers,  states  that  the  late  Prof.  Posepny  criticized 
him  for  looking  at  every  new  conception  in  ore-deposition 
''from  the  sole  standpoint  of  its  immediate  usefulness  in 
mining."  Mr.  Rickard  says  that  in  the  main  he  accepts 
the  impeachment.  One  might  almost  go  farther  than  this 
to-day  and  say  that  the  writer  on  ore-deposits  must  con- 
fine himself  to  noting  and  speculating  on  those  which  have 
economic  importance,  or  the  mass  of  literature  will  soon 
become  overwhelming.  In  the  following  notes,  therefore, 
those  occurrences  of  gold  which  have  proven,  or  under  fu- 
ture conditions  may  prove,  of  mining  value,  are  referred 
to.  Digressions  are  made  from  this  general  rule  of  treat- 
ment only  in  cases  where  the  gold  deposit  of  purely  scienti- 
fic interest  offers  special  features  for  comparison  with 
workable  ore-bodies. 

From  the  standpoint  of  personal  observation,  the  recent 
paper  of  Mr.  J.  E.  Spurr'  has  a  special  importance,  and 
portions  of  it  are  to  be  considered  as  a  distinct  contribu- 
tion to  the  assembly  of  information  concerning  ore  de- 
posits. Mr.  Spurr  has  in  this  paper  elaborated  the  theory 
advanced  by  him  to  account  for  certain  of  the  gold  veins 
of  the  Yukon  District  of  Alaska,*  and  has  cited  numerous 
occurrences  from  other  parts  of  the  world  in  support  of  his 
hypothesis.  As  I  understand  Mr.  Spurr  he  believes  that 
the  siliceous  relique  of  large  igneous  magmas,  as  exempli- 


"  T.  A.  Rickard,  "The  Formation  of  Bonanzas  in  the  Upper  Portions  of 
Geld  Veins."  Transactions  American  Institute  of  Mining  Engineers,  1901, 
Vol.  XXXL    p.   199. 

'  J.  E.  Spurr,  "A  Consideration  of  the  Igneous  Rocks  and  their  Segrega- 
tion or  Differentiation  as  related  to  the  Occurrence  of  Ores."  Transactions 
American  Institute  of  Mining  Engineers,  New  York  Meeting,  1902. 

*J.  E.  Spurr,  "Geology  of  the  Yukon  Gold  Belt."  i8th  Annual  Report 
United  States  Geological  Survey,  part  iii,  p.  300. 

-69- 


fied  in  the  consolidated  portions  now  visible  at  the  earth's 
surface,  is  more  prevalent  than  has>  generally  been  sup- 
posed. Further  he  maintains  that  in  any  large  area 
of  rocks,  which  is  characterized  by  the  occurrence  of 
metalliferous  deposits,  the  distribution  of  the  gold-bearing 
veins  is  connected  with  the  granite  or  siliceous,  rather 
than  with  the  more  basic  or  iron-bearing  portions  of  the 
mass.  Instead  of  stopping  with  a  granite  as  the  final 
phase  of  a  cooling  and  crystallizing  magma,  or  with  those 
forms  of  effusive  lava,  which  are  the  surface  equivalents 
of  granites,  he  goes  farther.  He  says  that  certain  portions 
of  the  cooling  mass  may,  if  they  find  a  sufficient  opening, 
take  the  form  of  very  siliceous  dikes,  which  by  the  disap- 
pearance of  the  biotite,  and  the  almost  complete  oblitera- 
tion of  the  feldspar,  become  what  he  has  called  ''alaskite." 
That  further,  by  the  disappearance  of  the  feldspar,  these 
alaskites  may,  and  do,  pass  into  quartz  veins,  containing 
precious  metals  as  direct  product  from  the  cooling  magma, 
and  among  these  metals  notably  gold.  In  other  words,  he 
traces  the  origin  of  certain  quartz  veins  directly  from 
igneous  magmas,  by  a  process  of  magmatic  segregation, 
and  derives  an  auriferous  quartz  vein  from  an  igneous 
siliceous  dike. 

Since  the  time  of  Hutton's  observations  on  igneous 
rocks,  and  the  experiments  of  Sir  James  Hall  in  the  latter 
part  of  the  eighteenth  century,  various  writers  have  held 
to  the  igneous  theory  of  veins.  J.  Brough  Smyth''  quotes, 
with  a  considerable  amount  of  favorable  comment,  a  work 
by  Thomas  Belt,"  in  which  an  igneous  theory  to  account 
for  the  origin  of  auriferous  quartz  veins  is  given  with  such 
compactness  that  I  venture  to  insert  it  here.  After  mak- 
ing the  general  statement  that  veins  are  explained  by  the 
theory  that  they  are  fissures  which  have  been  filled  with 
molten  silica  containing  entangled  metallic  vapors,  he  goes 
on  to  say  that  "the  fusion  of  rocks  in  the  bowels  of  the 
earth,  and  their  subsequent  consolidation  supply  the 
requisite  conditions  for  the  rending  open  of  the  superin- 

"J.  Brough  Smyth,  "Gold  Fields  and  Mineral  Districts  of  Victoria,"  1869, 
p.  236. 

•"Mineral  Veins — An  Enquiry  into  Their  Origin — Founded  on  a  Study 
of  the  Auriferous  Quartz  of  Victoria,"  by  Thomas  Belt 


cumbent  rocks,  and  the  filling  of  the  rents  so  formed  with 
fluid  matter,  varying  in  composition  according  to  the 
comparative  depth  from  which  it  has  been  projected." 

Although  the  ideas  of  the  earlier  investigators  were 
to  a  considerable  degree  speculative,  and  in  many  cases  not 
supported  by  the  detailed  observation  which  render  the 
theories  of  present  writers  worthy  of  attention,  still  a  con- 
sideration of  Mr.  Spurr's  theory  should  include  at  least  a 
mention  of  previously  advanced  theories  which  present  an- 
alogous features. 

Mr.  E.  D.  Levat'  has  called  attention  to  gold  occur- 
rences in  East  Siberia,  which  are  apparently  comparable 
to  some  extent  with  those  which  Mr.  Spurr  has  found  on 
the  Yukon.  I  have  not  seen  the  East  Siberian  deposits, 
but  shall  beg  indulgence  to  refer  to  them  before  proceeding 
to  the  description  of  localities  personally  visited.  The  de- 
scriptions given  are  evidently  the  result  of  much  patient 
investigation  on  the  part  of  the  French  engineer. 

On  a  tributary  of  the  Onon  River,  namely,  the  Khan- 
garok  Creek,  in  the  Trans-Baikal  region  to  the  southeast  of 
Irkutsk,  on  the  border  between  Siberia  and  Mongolia,  is 
situated  the  Blagovieshensk  placer.  This  mine  produced, 
in  the  years  from  1868  to  1879,  491  poods,  or  over  8,000 
kilograms,  of  alluvial  gold.  The  gravel  contains  0.25  per 
cent,  of  iron  pyrite,  which  on  being  assayed  was  found  to 
carry  $40  to  the  ton  in  gold.  The  bedrock  is  a  clay  schist 
lying  between  two  masses  of  granite  on  the  east  and  west. 
The  two  granite  masses  are  connected  by  a  dike  of  aplite, 
according  to  Mr.  Levat.  He  explains  the  occurrence  of 
this  rich  placer  from  the  erosion  of  the  aplite,  which  con- 
tains the  gold.  He  gives  it  as  his  opinion  that  the  aplite 
was  mineralized  by  a  process  contemporaneous  with  the 
disappearance  of  the  mica  from  the  igneous  rock,  and 
defines  the  aplite  as  a  granite  without  mica. 

In  an  entirely  different  locality,  that  of  the  Zeya  River, 
a  northern  tributary  of  the  Amoor  River,  Levat  states  his 
inability  to  find  auriferous  veins  or  other  primary  deposits 
to  account  for  the  existence  of  the  rich  placers  there  ex- 
ploited.   The  country  is  for  the  most  part  schist  and  gneiss 


'  E.  D.  Levat,  "L'Or  en  Siberie  Oriental,"  Paris,  1897. 


in  which  beds  of  quartz  are  interstratified.  There  is  a 
separate  large  detached  mass  of  fine  grained  granite.  In 
this  granite,  entirely  apart  from  any  other  rock,  occurs  the 
placer  deposit  forming  the  Zholon  Mine,  one  of  the  richest 
in  the  district.  It  is  situated  on  the  Zholon  Creek,  a  tribu- 
tary of  the  Zeya.  In  a  length  of  2.5  miles  along  this  creek 
more  than  $7,500,000  in  placer  gold  have  been  extracted.' 
The  gold  is  not  greatly  worn,  and  is  of  moderate  fineness 
of  grain.  The  granite  is  characterized,  especially  in  cer- 
tain areas,  by  a  schistosity,  running  nearly  north  and 
south,  the  minute  planes  being  filled  with  a  heavy  iron 
oxide.  No  quartz  is  found,  and  there  are  no  other  signs 
of  mineralization.  No  other  rock  occurs  in  the  vicinity. 
The  granite  on  assay  yielded,  even  in  its  best  mineralized 
portions,  less  than  $1  to  the  metric  ton  in  gold. 

The  above  cases  are  cited  as  illustrations  of  the  apparent 
direct  connection  of  gold  with  granitic  rocks  in  origin. 
One  can  hardly  question,  after  seeing  such  instances  in 
the  field  as  Mr.  Spurr  and  ]Mr.  Levat  call  attention  to,  that 
there  exists  a  genetic  connection  between  siliceous  rocks 
and  gold,  at  least  in  some  well-defined  instances.  Whether 
this  connection  of  gold  with  siliceous  provinces  is  of  such 
general  occurrence  as  !Mr.  Spurr  believes,  is  a  matter  sub- 
ject to  some  doubt,  and  worthy  of  investigation. 

That  rocks  of  a  moderately  siliceous  character  form 
a  habitat  for  gold-bearing  veins  has  frequently  been  re- 
marked. So  long  ago  as  1845  Mr.  P.  Tchihatchef  called 
attention  to  the  fact  that  the  occurrence  of  diorite  is  favor- 
able to  the  occurrence  of  gold,  and  gave  numerous  citations 
from  various  parts  of  the  world  in  support  of  this  view. 
In  1866  Mr.  P.  P.  Doroschin"  advanced  practically  the 
same  opinion.  Undoubtedly  the  association  is  of  very  fre- 
quent manifestation.  I  am  unable  to  believe,  however, 
that  either  diorite  or  granite,  in  single  occurrence,  without 
the  accompanying  presence  of  the  more  basic  rocks,  are 
generally  favorable  to  the  segregation  and  subsequent 
deposition  of  gold. 


*  From   1 890- 1 894  this  placer  paid  $2,000,000  in  dividends. 
«>?.  Tchihatchef,  "Voyage  Scientifique  dans  I'AItai  Oriental,"  Paris,  1845. 
""Archiv  fiir  w-ssenschaftliche  Kunde  in  Russland,"  vol.  25,   1866    (prob- 
able reference),  work  not  accessible. 


That  a  very  large  proportion  of  the  known  occurrences 
of  gold  are  directly  associated  with  silica  in  the  form  of 
quartz  must  be  admitted.  Until  within  very  recently  some 
investigators  have  claimed  that  an  original  deposit  of  gold 
without  quartz  was  an  unobserved  phenomenon.  Mr. 
Spurr,  as  I  understand  him,  maintains  that  the  derivation 
of  a  gold-bearing  vein  uninterruptedly  from  a  siliceous 
rock  is  not  only  a  possibility,  but  is  a  plausible  explana- 
tion for  many  of  the  occurrences  in  nature.  He  eliminates 
the  break  in  the  continuity  of  phenomena  which  is  a  neces- 
sary accompaniment  to  the  formation  of  a  vein  in  a  previ- 
ously existing  fissure.  Without  taking  up  here  the  various 
definitions  of  a  vein  which  have  been  advanced,  I  would 
suggest  that  Mr.  Spurr  has  rather  overlooked  the  physical 
side  of  the  question  in  his  desire  to  lay  stress  on  the  chemi- 
cal activity  involved.  If  the  occurrences  to  which  he 
draws  attention  are  quartz  segregations,  even  though  they 
contain  sulphides  of  the  metals,  and  are  payably  aurifer- 
ous, they  constitute  a  very  exceptional  class  of  veins,  ac- 
cording to  my  understanding  of  the  term.  Indeed,  I  ques- 
tion if  they  should  be  classed  as  veins  at  all.  I  would 
therefore  object  to  Mr.  Spurr's  views,  as  set  forth,  from 
two  standpoints — one  main,  one  subordinate.  From  the 
main  standpoint,  that  siliceous  rocks  without  the  accom- 
panying association  of  basic  rocks,  are  not,  in  the  major- 
ity of  observed  cases,  favorable  to  the  occurrence  of  gold ; 
and  from  the  subordinate  standpoint,  that  fissure-veins 
formed  by  siliceous  segregation  in  granitic  magmas  are 
difficult  to  conceive  of  from  a  purely  physical  standpoint. 

The  better  to  illustrate  my  meaning  as  regards  the  word 
vein,  I  cite  from  recent  geological  literature.  Prof.  J.  F. 
Kemp,  in  his  generally  clear  and  useful  paper,  "The 
Role  of  the  Igneous  Rocks  in  the  Formation  of  Veins,"^^ 
appears  to  me  to  use  the  term  vein  in  an  ambiguous  sense, 
in  his  description  of  pegmatitic  occurrences.  Referring 
to  certain  cases  in  Connectitcut,  he  says,  "Pegmatites 
grade  insensibly  into  quartz-veins."  Such  a  phenomenon, 
except  in  a  very  limited  sense,  is  hard  to  reconcile  with 
the  accepted  definition  of  a  fissure-vein.     Pegmatite  de- 

^^J.  F.  Kemp,  Transactions,  American  Institute  of  Mining  Engineers,  \'oL 
XXXI.,  p.  183. 

—  73  — 


posits  undoubtedly  occur  with  well  defined  walls.  I  am 
informed  by  Mr.  Philip  Argall  that  dikes  of  pegmatite,  ex- 
hibiting sharp  walls,  occur  well-defined  in  the  granites  of 
Gilpin  and  Clear  Creek  counties,  Colorado.  In  a  recent 
paper  on  the  occurrence  of  mica  in  Brazil."  Mr.  H.  Kil- 
burn  Scott  says,  "The  principal  mica  deposits  are  peg- 
matite veins,  lenses  or  dikes,  which  occur  in  the  metamor- 
phic  schists,"  etc.,  and  states  that  the  veins,  running 
parallel  to  one  another,  from  20  ins.  to  10  ft.  in  width,  may 
be  traced  for  long  distances.  Masses  or  bosses  of  quartz 
occur  in  the  midst  of  these  pegmatite  veins.  While  grant- 
ing the  existence  of  pegmatite  veins  of  considerable  length 
and  clear-cut  definition,  I  maintain  that  they  are  excep- 
tional, and  that  the  normal  pegatite  occurrence  exhibits 
the  characteristic  features  of  a  segregation  from  the  en- 
closing mass,  its  structure  grading  into  that  of  the  con- 
taining granite  by  a  finer  and  finer  crystallization. 

For  example  at  the  well-known  tourmaline  deposit  of 
Paris,  Maine,  the  occurrence  is  a  pegmatitic  segregation 
in  granite.  The  mass  lies  in  the  granite  with  no  well- 
defined  boundaries.  It  could  not  be  defined  as  a  vein  or 
dike.  The  gangue  minerals  common  to  quartz  veins  occur 
in  it,  exhibiting  many  of  the  features  of  arrangement 
characteristic  of  such  veins.  Quartz  crystals,  arranged  in 
comb-structure,  and  with  open  druses,  even  metallic  sul- 
phides, occur.  I  see  no  reason  to  doubt  that  the  presence 
of  gold  in  minute  quantities  might  be  established.  In  the 
midst  of  the  Paris  deposit  occur  many  secondary  and 
tertiary  fractures,  which  appear  to  have  been  filled  and 
refilled  with  quartz  crystals.  Some  of  these  veinlets  pene- 
trate even  the  big  crystals  of  black  tourmaline,  which  I 
have  seen  15  ins.  in  length,  and  4  ins.  in  diameter.  But 
taken  as  a  whole,  the  occurrence  is  no  more  a  vein  than 
are  the  elongated  blebs  of  magnetite,  which  compose  many 
of  the  iron  deposits  in  the  gneisses  of  New  Jersey.  Veins 
in  an  extremely  local  manifestation  are  formed  as  a  sub- 
ordinate phenomenon  in  connection  with  pegmatite  de- 
posits, as  illustrated  at  Paris,  fulfilling  all  the  requisite 


"  H.  Kilburn  Scott,  "On  the  occurrence  of  Mica  in  Brazil  and  on  its 
preparation  for  the  Market,"  Proceedings,  Institution  of  Mining  and 
Metallurgy,  April  23,  1903. 

—  74  — 


conditions  of  a  pre-existing  fissure.subsequently  filled  by 
extraneous  material.  They  are,  however,  in  the  majority 
of  cases,  of  interrupted  continuity,  of  extremely  irregular 
width,  and,  except  in  rare  instances,  of  negligible  import- 
ance from  a  mining  standpoint. 

Mr.  Spurr,  referring  to  the  deposits  of  gold  at  Bere- 
zovsk*^  in  Russia,  says  the  veins  ''generally  stretch  across 
the  dikes  at  right  angles  to  the  walls  and  have  been  con- 
sidered as  filling  'fissures  of  contraction'  by  Posepny.^* 
This  is  probably  correct,  for  the  veins  follow  the  same 
lines  as  the  'columnar  jointing'  of  dikes,  which  are  due 
to  contraction." 

This  explanation  of  Posepny's  regarding  the  veins  at 
Berezovsk  appears  to  me,  with  all  due  respect  to  the  views 
held  by  that  renowned  student,  as  probably  highly  incor- 
rect. The  country  rock  at  Berezovsk,  which  is  situated  7 
miles  to  the  northeast  of  Ekaterinburg,  Perm  Government, 
Russia,  is  a  part  of  a  large  area  of  granites  and  metamor- 
phic  schists  occupying  the  south  central  part  of  the  Perm 
Government.  At  Berezovsk  itself  the  country  consists  of 
a  muscovite  granite  in  more  or  less  schistose  bands,  inter- 
calated with  mica  schist.  In  the  immediate  vicinity  of  the 
village  is  an  unusually  large  area  of  pure  granite,  of  fine 
texture,  while  the  associated  schist  is  subordinate  in 
amount.  The  schistosity  of  the  whole  runs  north  and 
south.  To  the  west,  but  within  the  crystalline  area,  are 
patches  of  a  peculiar  rock,  which  has  frequently  a  curious 
green  color,  and  which  is  probably  a  metamorphosed  dolo- 
mitic  limestone.  This  consists  of  magnesite,  siderite  and 
calcite,  and  is  called  listvenite.  The  richest  gold  ore  which 
has  been  worked  occurs  close  to  Berezovsk.  The  alternat- 
ing bands  of  schist  and  granite  have  been  at  one  time 
fractured  by  fissures  having  a  direction  N.  80°  E.,  which, 
although  they  penetrate  all  the  rocks  except  certain  basic 
dikes,  have  their  strongest  manifestation  in  the  granite. 

^3  Berezovsk,  pronounced  Beryozoovsk,  from  the  word  Beryoza,  birch  tree. 

1*  Posepny  states  that,  although  the  fissures  at  Berezovsk  cannot  be  as- 
cribed to  structural  dislocation,  nevertheless  in  the  Pishminsk  district  (20 
miles  to  the  west),  he  found  the  gold  quartz  veins  occupying  the  same 
position  as  in  the  peculiar  Berezovsk  granite,  and  suggests  caution  in  re- 
ferring the  veins  of  Berezovsk  to  local  filling  from  the  granite,  I  did  not 
see  east  and  west  veins  in  the  Pishminsk  District,  but  saw  them  at  Moor- 
zinsk,  as  noted  farther  on.  See  F.  Posephy,  "The  Genesis  of  Ore  De- 
posits," Transactions  American  Institute  of  Mining  Engineers,  1893,  Vol. 
XXIII,  p.  266. 

—  75  — 


Into  the  fissures  the  gold-bearing  solutions  appear  to  have 
penetrated,  resulting  in  the  formation  of  the  veins.  In 
connection  with  the  Berezovsk  deposits  occur  bands  of  ser- 
pentine representing  metamorphosed  basic  dikes.  The 
quartz  veins,  which  are  rarely  over  3  ins,  in  width,  and 
from  6  ins.  to  2  ft.  apart,  penetrate  all  the  rocks  except  the 
bands  of  serpentine,  and  it  is  reasonable  to  infer  that  the 
basic  dikes'  were  the  direct  agents  of  mineralization. 

In  former  times,  when  slave  labor  was  employed,  the 
Berezovsk  deposit  was  developed  by  about  6,000  ft.  of 
drifting  and  stoping,  and  I  was  enabled,  through  the  cour- 
tesy of  the  present  manager,  Mr.  Sokolof,  to  inspect  these 
old  workings.  The  mine  is  at  present  worked  in  places, 
but  the  low-grade  ores  formerly  extracted  cannot  now  be 
profitably  handled.  It  is  stated  that  the  richest  of  the 
small  veins  carried  I  oz.  in  gold,  while  the  average  for 
the  ore  as  mined  was  0,25  oz.  The  average  of  the  entire 
stock  or  wide  belt  of  berezite,"  as  proved  by  recent  samp- 
ling, is  o.  I  oz.  in  gold  per  ton,  and  it  has  been  determined 
that  appreciable  though  not  workable  amounts  of  gold  oc- 
cur throughout  the  granite  area  for  a  width  of  several 
miles.  The  ore  taken  from  the  selected  portions  of  the 
leads  now  being  worked,  is  milled  by  stamps,  thirty  in 
number,  with  accompanying  amalgamation,  followed  by 
Chilean  mills,  and  the  tailings  directly  cyanided. 

The  granite,  called  in  its  more  mineralized  portions, 
berezite,  consists  of  quartz,  feldspar  and  muscovite.  It  is 
impregnated  with  iron  pyrite,  and  is  subject  to  much  local 
silicification.  The  examination  of  the  granite  by  Arzruni, 
referred  to  by  Mr.  Spurr,  is  susceptible  of  more  than  one 
interpretation.  The  disappearance  of  feldspar  can  take 
place  normally  by  sericitization,  as  shown  by  Mr.  Lind- 
gren'",  and  as  I  have  tried  to  show,"  and  in  the  berezite 
deposit  subordinate  silicification  has  evidently  occurred. 


^^Mr.  A.  Karpinski  states,  iCompte  Rendu,)  Congres  Geologique  Inter- 
national, 7  me.  Session,  St.  Peterbourg,  1897,  p.  ccix,  that  berezite,  "in  its 
typ'ical  form,  consists  of  muscovite  and  of  quartz  with  a  mixture  of  pyrite; 
it  is  a  rock  of  secondary  origin,  formed  by  the  transformation  of  micro- 
granite  and  of  granite." 

"  W.  Lindgren,  "The  Gold  Quartz  Veins  of  Nevada  City  and  Grass 
Valley,"  17th  Annual  Report  United  States  Geological  Survey,  pt.  ii.,  p.  148. 

'^'  C.  W.  Purington,  "Preliminary  Report  on  the  Afining  Industries  of  the 
Telluride  Quadrangle,  Colo.,"  18th  Annual  Report  United  States  Geological 
Survey,  pt.  iii,  p.  807. 

—  76  — 


I  am  inclined  to  disbelieve  the  efficacy  of  any  tests  which 
have  been  made  on  the  Ural  berezite,  with  the  view  of 
proving  its  primarily  auriferous  character.  The  difficulty 
of  getting  a  piece  of  it,  which  is  not  penetrated  by  one 
or  more  of  the  innumerable  quartz  stringers  resulting 
from  ore  impregnation,  is  great.  The  granite  area  itself  is 
large,  and  the  area  of  mineralization,  so  far  as  my  observa- 
tions have  led  me  to  believe,  is  very  much  larger.  In  a 
well  sunk  in  the  yard  of  Mr.  W.  E.  Davidson  in  Ekaterin- 
burg, decomposed  greis en-like  material  was  found,  result- 
ing from  the  disintegration  of  the  schistose  granite,  on 
which  the  city  of  Ekaterinburg  is  built.  I  collected  some 
of  the  material  from  the  bottom  of  this  well,  and  panned 
gold  from  it.  I  also  panned  gold  from  the  decomposed 
material  lying  on  the  granite  in  the  immediate  outskirts 
of  Ekaterinburg,  and  many  little  pits  may  be  seen  near  the 
city,  in  the  beds  of  the  runs  tributary  to  the  river  Isset, 
where  the  peasants  have  washed  gold. 

In  the  cuts  of  the  Perm-Tiumen  Railway,  to  the  north 
of  Ekaterinburg,  exposures  of  the  granite  may  be  seen 
which  appear  fresh  and  unmineralized.  But  on  close 
examination,  pyrite  crystals  are  generally  visible,  and 
quartz  veins  are  not  uncommon.  Quartz  veins  and  miner- 
alized streaks,  characterized  by  an  oxidized  appearance, 
may  be  seen  penetrating  the  granite  close  to  the  cathedral 
in  the  town  of  Ekaterinburg  in  the  public  square  situated 
between  the  telegraph  office  and  the  American  Hotel.  I 
give  the  above  observations  in  order  to  indicate  how  wide- 
spread is  the  mineralization  and  how  nearly  impossible 
it  would  be  to  obtain  a  piece  of  this  granite  remote  from 
the  proximity  of  a  quartz  vein. 

As  regards  the  Assuring  at  Berezovsk,  there  is  much 
evidence  to  show  that  the  fractures  are  not  of  local  de- 
velopment, and  that  the  N.  So**  E.  fracturing,  contempo- 
raneous with  another  system  which  strikes  N.  30**  W.,  is 
of  widespread  areal"  manifestation.  In  an  open  cut  near 
the  village  of  Berezovsk,  the  two  sets  of  fissures,  both 
sharply  defined  and  carrying  veins  of  auriferous  quartz, 
may  be  seen.    At  other  localities,  from  5  to  75  miles  dis- 

"  Note  the  observations  of  Posepny  before  recorded. 

—  77  — 


tant,  for  example  at  the  Moorzinsk  concession,  5  miles 
to  the  north,  at  emerald  mines  of  the  Crown  Do- 
main, 50  miles  to  the  east,  and  in  tHe  Serebransk  Dacha, 
75  miles  to  the  northwest,  the  fissuring,  conformable  in 
direction  to  that  at  Berezovsk,  is  so  well  exemplified  that 
there  can  remain  no  doubt  of  its  being  a  general  and  not  a 
local  phenomena.  The  data  here  given  might  be  consider- 
ably extended,  but  the  evidence,  I  think,  is  sufficiently 
strong  to  show  that  the  direction  of  the  veins  at  Berezovsk 
are  determined  by  contemporaneous,  widespread  systems 
of  fracturing,  and  it  is  justifiable  to  conclude  that  the  pro- 
visional statement  of  Posepny  regarding  the  origin  of  the 
fissures  at  Berezovsk  is  unworthy  of  consideration. 

I  have  shown  that  at  Berezovsk  basic  dikes  occur  which 
are  themselves  not  penetrated  by  ore,  but  which  have  an 
influence  on  the  values  which  are  found  in  the  veins  of  the 
granite  and  the  schist.  O^e  cannot  doubt  that  the  granite 
must  have  been  rigid  to  admit  of  fissuring.  The  basic 
dike  intrusions  occurred  subsequently  to  the  solidifying  of 
the  granite.  The  probability  is  that  the  ore-impregnation 
and  filling  were  contemporaneous  with,  or  directly  conse- 
quent on,  the  intrusion  of  the  dikes.  The  remarkable 
changes  which  have  taken  place  in  the  bordering  limestone, 
causing  the  change  into  listvenite,  is  another  evidence  of 
the  widely  manifested  metamorphic  action  of  the  basic 
dikes.  In  short,  the  gold  deposits  in  the  vicinity  of  Bere- 
zovsk present  nothing  extraordinary.  It  appears  to  me  an 
analogous  occurrence  to  the  Alaska-Treadwell  Mine,  on 
Douglass  Island,  Alaska."  There  the  mass  or  wide  dike 
of  sodium  syenite  has  been  mineralized  throughout,  con- 
sequent on  the  intrusion  of  a  much  later  dike  of  basalt.  I 
have  examined  many  microscopic  slides  of  the  Treadwell 
ore,  both  of  the  rich  and  poor  varieties,  and  have  failed  to 
find  one  case  in  which  minute  stringers  of  quartz  connected 
with  pyrite  crystals  do  not  occur.  The  deposit  exhibits  all 
the  features  of  a  shattered  and  subsequently  cemented  and 
impregnated  mass.  The  Berezovsk  deposit  presents  a  near 
corollary  to  the  Treadwell,  the  difference  being  that  the 


"G.  F.  Becker,  "The  Gold  Fields  of  Southern  Alaska,"   i8th  Annual  Re- 
port United  States  Geological  Survey,  pt.  iii.,  p.  64. 

—  78  — 


dike  rocks  were  considerably  older  at  Berezovsk  and  the" 
concentration  of  the  gold  values  was  considerably  less.  I 
have  seen  many  of  the  openings  on  quartz  veins  in  the 
Perm  Government  of  Russia,  and  have  reached  the  con- 
clusion that,  so  far  as  the  gold  deposits  are  concerned,  there 
has  been  a  permeation  to  an  extraordinary  areal  extent  of 
gold-bearing  solutions  into  a  previously  shattered  and 
fissured  country.  The  result  has  been,  especially  in  the 
district  of  which  the  city  of  Ekaterinburg  forms  the  ap- 
proximate center,  the  formation,  if  it  may  be  so  expressed, 
of  one  great  body  of  gold-bearing  material,  so  low  grade 
that  it  is  not,  except  in  certain  very  limited  areas,  of  eco- 
nomic importance.  The  cause  of  this  permeation  is  to  be 
laid  at  the  door  of  the  basic  dikes  and  stocks  which 
occur  in  various  parts  of  the  region  rather  than  to  the  rocks 
of  granitic  type  which  were  earlier  formed. 

Taking  the  Ural  as  a  whole,  it  is  evident  that  the  dis- 
tribution of  the  gold  deposits  follows  with  a  considerable 
degree  of  regularity  that  of  the  very  basic  rocks.  At 
Miassky  Zavod,  on  the  Trans-Siberian  Railway,  in  the 
Orenburg  Government,  where  the  gold  deposits  have 
proved  exceptionally  rich,  as  evidenced  by  the  workings  of 
many  years,  and  where  payable  deposits  are  still  operated, 
the  region  is  characterized  by  a  large  area  of  granite  with 
associated  peridotite.  Extending  to  the  south,  it  is  notice- 
able that  the 'belt  of  peridotites,  greenstone  schists  and 
porphyrites,  making  to  the  southwest,  is  characterized  by^ 
the  occurrence  of  gold  as  far  as  Verkni-Uralsk,  a  distance 
of  nearly  lOO  miles.  On  the  other  hand,  the  belt  of  more 
acid  crystalline  schists,  and  the  granite  area  to  the  west, 
are  for  the  most  part  singularly  barren  of  gold  values.  The 
only  exception  in  the  granite  area  in  Kotchkar,^"  where 
in  the  midst  of  an  immense  area  of  granite,  extending  in 
all  directions,  occur  two  small  stocks  of  peridotite  cutting 
through  it.  The  more  southerly  of  these,  which  is  about 
two  miles  in  length,  is  marked  by  the  occurrence  of  gold 
deposits,  in  veins  far  richer  than  the  veins  of  any  of  the 
surrounding  area.    It  is  the  direct  influence  of  the  perido- 

»H.  B.  C.  Nitze  and  C.  W.  Purington,  "The  Kotchkar  Gold  Mines,  Ural 
Mountains,  Russia,"  Transactions  American  Institute  Mining  Engineers, 
Vol.  XXVIIL,   1898,  p.  24. 

—  79  — 


tites  which  has  caused  the  auriferous  values  in  the  veins 
which  now  cut  the  enclosing  granite.  One  has  only  to 
consult  Sheet  139  of  the  Geological  Map  of  European  Rus- 
sia, prepared  by  the  Geological  Committee  of  St.  Peters- 
burg (Vol.  Ill,  No.  2,  1886)  to  note  the  correlation  of  the 
iron-bearing  rocks  with  the  more  prominent  gold  deposits. 
The  occurrence  of  ilmenite,  chromic  iron,  magnetite  and 
other  ultra-basic  minerals  at  Miass,  in  the  Ilmen  Moun- 
tains, at  Magnitnaia  Stantsia,  and  other  points  in  the  gold 
belt,  is  not  to  be  thrown  out  of  consideration,  when  one  is 
studying  the  association  of  the  gold.  At  Miass  I  found  it 
to  be  a  well-proven  rule  of  prospecting  among  the  Kazak 
tributers  or  ''siaratels,"  that  there  is  a  constant  increase  in 
the  amount  of  placer  gold,  and  presumably  in  the  vein 
gold,  from  the  granites  and  acid  crystalline  schists  of  the 
east  toward  the  Igish  Mountains  on  the  west,  which  are 
composed  of  greenstone  schist,  Dorphyrite,  serpentine  and 
peridotite. 

On  page  39  of  this  paper,  Mr.  Spurr  says :  "By  apply- 
ing the  idea  of  the  change  of  senfregated  metals  with  the 
progress  of  general  rock-segregation,  some  light  on  min- 
eral association  and  successior  ^nay  possibly  be  obtained. 
For  example,  in  many  distncts  of  the  world  gold  and 
platinum  are  closely  associated  in  places.  In  these  dis- 
tricts it  is  usual  to  find  extremely  acid  and  extremely  basic 
rocks  (complementary  varieties)  intimately  associated, 
representing  apparently  an  extreme  stage  of  rock-segrega- 
tion ;  and  frequently,  as  in  the  Urals,  the  platinum  is  found 
to  be  derived  from  the  basic  re  .ks  (peridotites),  and  the 
gold  chiefly  from  gold-quartz  veins  in  the  siliceous  ones 
(granite).     This  is  one  of  the  simplest  cases." 

I  have  already  tried  to  bring  out  the  fact  that  the  gold 
in  the  Ural  is  for  the  most  part  dependent  for  its  occur- 
rence on  the  distribution  of  the  basic  rocks,  and  I  am  not 
inclined  to  believe  that  the  platiniferous  areas  of  that  part 
of  Russia,  where  gold  also  occurs,  offer  any  exception  to 
the  general  phenomena  which  obtain.  I  agree  with  Mr. 
Spurr  that  the  association  of  gold  and  platinum  deposits, 
which  he  assumes  to  occur  in  the  Ural,  represents  one  of 
the  simolest  cases  of  allied  rock  and  metallic  segregation, 

—  80  — 


but  it  is  scarcely  justifiable  to  dispose  in  an  off-hand  man- 
ner of  a  great  area  of  metalliferous  territory  in  which  oc- 
cur some  of  the  most  remarkable  mineral  associations 
which  have  been  met  with  in  the  known  world. 

In  the  Goroblagodat  region  of  the  Ural,  the  most  im- 
portant deposits  of  platinum  occur."  The  gold  associated 
with  platinum  in  these  deposits  is  derived  from  the  same 
general  rock  area.  This  area  includes  the  basins  of  the 
Iss  and  Viya  rivers,  tributaries  of  the  Tura.  The  rocks  in 
it  consist  of  diorite,  gabbro,  peridotite,  serpentine,  por- 
phyrite,  syenite  and  limestone.  There  is  no  granite  with- 
in the  area  drained  by  the  Iss,  so  far  as  has  been  deter- 
mined, and  it  will  be  noticed  on  Prof.  Zaitseff's^^  map, 
which  I  have  reproduced,"^  that  the  basic  rocks  are  in 
larger  proportion  in  the  platiniferous  areas  of  the  two 
rivers.  The  gold  occurs  in  the  placers  of  the  Iss  in  the 
proportion  of  from  i  to  25  per  cent,  by  weight  to  the  plati- 
num, while  the  ratio  becomes  more  nearly  equal  as  the 
distance  from  the  source  of  the  platinum  increases.  In 
the  Tura,  where  the  gravel  is  now  worked  by  means  of 
dredging,  the  proportion  of  gold  to  platinum  is  from  1-5 
to  2-5  by  weight.  The  source  of  the  platinum  has  been 
determined  to  be  in  the  rocks  through  which  the  Iss  and 
Viya  cut  their  beds,  and  it  must  be  assumed  that  the 
source  of  the  gold  is  in  the  same  area.  Prof.  Zaitseff'*  in 
his  detailed  descriptions  of  the  placers  on  the  Viya  River, 
in  the  vicinity  of  Mount  Kachkanar,  makes  it  clear  that 
the  proportion  of  gold  is  larger  than  in  the  Iss,  and  it  is 
likely  that  this  accounts  for  the  larger  amount  of  associ- 
ated placer  gold  in  the  lower  reaches  of  the  Tura.  As 
Mount  Kachkanar  is  composed  of  peridotite  entirely  and 
as  peridotite  is  the  igneous  rock  in  the  vicinity  far  in  ex- 
cess of  any  other,  it  is  reasonable  to  infer  that  the  gold  is 
more  dependent  on  that  rock  than  on  any  in  the  district. 
He  refers  to  veins  of  quartz  occurring  in  the  region,  and 
states  that  in  many  cases  the  gold  and  platinum  exhibit 

^  C.  W.  Purington,  "The  Platinum  Deposits  of  the  Tura  River  System, 
Ural  Mountains,  Russia,"  Transactions  American  Institute  Mining  Engi- 
neers, Vol.  XXIX.,  1899,  p.  3. 

22"Die  Platinlagerstatten  am  Ural,"  A.  Zaitseff,  Tomsk,   1898. 

23  C.  W.  Purington,  op.  cit. 

'*  Zaitseflf,  op.  cit.,  p.  30. 


little  rounding,  and  could  not  have  traveled  far  from  the 
original  source.  In  samples  of  the  alluvial  gold  and  plati- 
num which  I  v^ashed  from  the  Tura"^  during  the  summer 
of  1902,  there  is  no  great  difference  in  the  amount  of  abra- 
sion which  the  two  metals  have  suffered.  The  platinum 
grains  are  rougher,  as  would  be  expected  from  the  greater 
hardness.  I  would  infer  that  the  two  metals  are  derived 
from  sources  not  far  apart.'" 

Another  example  of  the  association  of  gold  and  plati- 
num is  worthy  of  being  cited.  In  the  spring  of  1901  I 
had  the  opportunity  of  examining  a  placer  mine  situated 
on  Althouse  Creek,  a  tributary  of  the  Illinois  River,  in 
Josephine  County,  Oregon.  The  rocks  of  the  district, 
which  is  drained  by  the  Althouse  Creek,  are  almost  entire- 
ly of  a  basic  nature,  and  a  limited  amount  of  diorite  repre- 
sents the  only  moderately  siliceous  rock.  Serpentines  and 
chloritic  schists,  with  which  is  associated  a  considerable 
amount  of  bedded  massive  chrome-iron  garnet,"^  are  the 
prevailing  rocks.  Gold-bearing  veins  of  irregular  size 
and  distribution  cut  these  rocks,  and  are  known  to  the 
miners  as  "pockety."  It  is  from  these  veins  that  the  gold 
of  the  placers  is  derived.  In  a  clean-up  of  the  placer  gold 
at  which  I  assisted,  50  oz.  of  gold  were  recovered,  asso- 
ciated with  which  was  0.5  oz.  of  platinum,  w^th  some  os- 
miridium.  The  r;old  exhibited  the  characteristic  results 
of  attrition,  as  did  the  platinum  to  a  less  degree,  but  it  was 
evident  that  the  sources  from  which  the  two  metals  had 
been  derived  were  near  at  hand,  and  not  greatly  removed, 
one  from  another.  The  region  of  southwestern  Oregon  is 
pre-eminently  one  of  basic  rocks,  with  associated  metal  de- 
posits, such  as  nickel,  cobalt,  platinum,  which  one  would 
expect  to  occur  in  such  an  area.  Many  gold  placers  are 
w^orked  there,  and  a  few  veins  are  being  opened  in  the  ser- 
pentines and  chloritic  schists. 

]Mr.  Spurr  says :    "The  intimate  genetic  connection  of 


»  From  the  Yerosalinski  Placer,  4  miles  above  the  bridge  where  the  post 
road  to  Bogoslovsk  crosses  the  Tura. 

280wing  to  the  impurities  which  are  combined  with  the  platinum,  its 
specific  gravity,  in  its  alluvial  occurrence,  may  be  reckoned  as  practically  the 
same  as  that  of  the  gold. 

^  Determined  for  me  through  the  courtesy  of  Dr.  Charles  Palache,  of 
Harvard  University.  This  material  has  recently  been  referred  to  in  several 
mining  journals  as  jade. 

—  82  — 


these  typical  gold-quartz  veins  with  distinctly  basic  rocks, 
such  as  those  of  the  diabasic  family,  may  be  safely  called 
exceptional."  I  make  bold  to  maintain  that  the  associa- 
tion of  gold-bearing  quartz  veins  of  normal  type  with 
rocks  of  extremely  basic  character,  from  which  often  a 
genetic  connection  may  be  reasonably  inferred,  is  by  no 
means  exceptional.  In  the  Guianas  of  South  America, 
one  of  the  cases  quoted  by  Mr.  Spurr  from  Phillips  and 
Louis  (Ore  Deposits),  in  support  of  his  hypothesis,  inves- 
tigations have  shown  that  the  occurrence  of  gold  is  not 
dependent  on  the  distribution  of  the  granite,  but  on  that  of 
the  diabase.  Messrs.  Quelch  and  Harrison,  the  geolo- 
gists of  the  British  Government  at  Demerara,  informed  me 
in  conversation  that  the  gold,  at  any  rate  in  Demerara,  is 
dependent  on  the  diabase  which  penetrates  the  granite  and 
the  other  rocks  of  the  country  in  dikes.  Mr.  J.  D.  Harri- 
son, in  a  published  report,""*  says :  "The  acidic  rocks  of  the 
district,  whether  gneiss,  granite  or  porphyrite,  do  not  ap- 
pear to  be  the  original  sources  of  practically  any  of  the 
gold  of  the  auriferous  gravels  of  the  district,  which  have 
probably  all  been  derived  from  the  basic  rocks,  either  the 
diorite,  the  older  intrusive  rocks  now  epidiorite  and  horn- 
blende schist,  or  the  diabase,  or  from  parts  of  the  acidic 
rocks  impregnated  with  the  metal  by  percolating  water 
during  their  intrusions.  The  parts  of  the  diabase  rocks 
which  are  the  richer  in  the  iron  ores  and  especially  in 
pyrites  are  also  the  richer  in  content  of  gold." 

In  the  spring  of  1899  I  had  the  opportunity  of  making 
observations  in  the  gold  fields  of  the  Saramacca  River  in 
Dutch  Guiana.  The  country  was  for  the  most  part  slate 
and  schist,  and  the  only  igneous  rock  found  over  an  area 
of  50  square  miles  was  diabase.  Auriferous  veins  were 
found  in  slate  intercalated  with  the  schistosity.  The  gold 
obtained  in  Suriname  is  mostly  of  alluvial  character,  and 
that  of  the  Saramacca  field  is  no  exception.  Little  oppor- 
tunity was  afforded  for  noting  the  appearance  of  the  veins. 
It  is  worthy  of  note,  however,  that  in  the  richest  of  the 
placer  ground  which  was  examined  the  bedrock  was  dia- 


23  J.    D.    Harrison,    "Report    on    the    Geology    of    the    Essequibo,    Potaro, 
Konawaruk,  and  Demerara  Rivers,"  Georgetown,  Demerara,   1900,  p.  69. 

—  83  — 


base.  The  peculiar  rough  and  unworn  appearance  of  the 
gold  of  the  Guianas  appears  to  preclude  the  belief  that  it 
has  moved  a  great  distance  from  its  original  habitat  in  the 
veins.  The  patchy  character  of  its  occurrence  is  also  evi- 
dence along  the  same  line.  If  one  believes  that  this  gold 
originated  in  quartz  veins  one  must  admit  that  it  has  trav- 
eled no  great  lateral  distance,  and  may  therefore  argue 
with  some  reason  from  the  underlying  rock  as  to  the 
nature  of  the  rock  which  was  originally  associated  with 
its  veins. 

In  the  Yenesei  District  of  Siberia,  to  the  east  of  the 
Yenesei  River,  and  to  the  north  of  its  tributary  the  An- 
gara, I  visited  several  of  the  principal  gold-bearing  areas 
in  the  summer  of  1898.  The  country  for  the  most  part, 
on  the  Tala,  Uderei  and  Boorovaya  creeks,  tributaries  of 
the  Angara,  is  slate  and  contorted  schist,  of  argillaceous 
and  carbonaceous  character.  There  are  smaller  areas  of 
sandstones  and  metamorphic  limestone.  The  rocks  are 
penetrated  in  all  directions  by  quartz  veins,  from  which  it 
seems  highly  probable  that  the  gold  of  the  placers  has  been 
derived.  These  placers  are  now  practically  worked  out, 
but  in  view  of  their  not  inconsiderable  product  (26,530 
poods,  or  434,030  kilograms,  roughly,  $225,000,000  in 
gold),"  and  the  remarkably  simple  rock  association,  I  con- 
sider the  region  worthy  of  mention  in  the  present  discus- 
sion. The  only  igneous  rocks  seen  in  the  course  of  300 
miles  of  journeyings  in  the  Yenesei  District  were  basic 
rocks,  resembling  peridotite.  On  the  Boorovaya  Creek, 
at  the  property  of  Mr.  Goodkof,  75  miles  to  the  north  of 
the  river  Angara,  dikes  of  peridotite  were  seen  cutting  the 
slates,  and  large  boulders  of  peridotite  appeared  in  the 
gravel  dumps.  Boulders  of  this  very  basic  rock  were  seen 
in  many  of  the  placers  of  the  Uderei  and  tributary  streams, 
but  only  in  the  instance  cited  was  the  rock  seen  in  place. 
Granite  was  not  found,  and  diorite  only  in  a  few  instances. 
I  am  not,  of  course,  prepared  to  say  that  large  areas  of 
siliceous  rocks  do  not  exist  in  the  Yenesei  District,  but  the 
alluvial  material  of  the  placers  does  not  testify  to  their 


»M.    Shostak,    "Gold    Mining    Industry   of  the   Tomsk   Mining   District,* 
Tomsk,  1896,  p.   10. 

-84- 


presence.  The  evidence  seems  to  point  to  the  pendotite 
as  the  rock  with  which  the  gold  was  genetically  connected, 
if  one  is  to  believe  its  origin  due  to  the  influence  of  any 
igneous  rock. 

As  Mr.  Spurr  has  himself  called  attention  to  the  Appa- 
lachian gold  region,  it  is  proper  to  refer,  in  a  discussion  of 
his  paper,  to  the  interesting  occurrence  at  the  Haile  Gold 
Mine  in  South  Carolina,  which  has  been  several  times  de- 
scribed.^" I  have  made  several  visits  to  this  property,  and 
no  clearer  case  has  come  to  my  notice  of  the  association  of 
gold  ore  with  basic  dike  rocks.  Situated  in  an  ear  of 
hydro-mica  schists,  now  silicified  by  the  influence  of  the 
ore-bearing  solutions,  the  principal  mine  workings  are 
found  to  follow  closely  dikes  of  diabase.  These  dikes  all 
cut  the  rocks^  and  it  is  in  the  silicified  slat?e  bands,  directly 
in  contact  with  the  dikes,  that  the  best  ore-shoots  occur. 
As  one  gets  away  from  the  dikes,  the  values  in  the  veins 
decrease.  In  the  southern  Appalachians  in  general,  where 
gold-bearing  quartz  veins  occur,  dikes  are  almost  a  con- 
stant phenomenon.  They  are  in  most  cases  of  a  basic 
character,  those  of  siliceous  make-up  being  exceptional. 

In  discussing  the  southern  Appalachians,  I  would  call 
attention  to  one  statement  made  by  Mr.  Spurr  in  his  gen- 
eral summing  up.  It  appears  to  me  that  he  has  fallen  into 
an  error  from  the  fact  that  he  has  failed  to  keep  in  mind 
the  physical  characteristics  of  a  vein.  He  says:  "It  is 
recognized  that  the  metals  (in  the  Appalachians),  though 
present,  are  constantly  far  less  abundant  than  in  the  Cor- 
dilleran  region."  This  is  true.  It  is  not  true,  however, 
as  Mr.  Spurr  affirms,  that  a  vein  discovered  in  the  Appa- 
lachians will  "directly  peter  out."  The  chances  are  that 
ore  found  in  the  region  will  prove  of  very  low  grade,  as 
at  Dahlonega,  or  of  a  pockety  character.  The  veins  are, 
however,  as  continuous  in  length  as  in  most  mining  re- 
gions, and  they  have  in  some  instances  been  worked  to  a 
considerable  depth.  If  in  the  southern  Appalachian  gold 
belt  it  is  found  that  one  of  the  intercalated  lenses  of  quartz 

^  G.  F.  Becker,  "Gold  Fields  of  the  Southern  Appalachians,"  United 
States  Geological  Survey,  i6th  Annual  Report,  pt.  iii,  p.  306.  Also  H.  B. 
C.  Nitze  and  H.  A.  J.  Wilkins,  "The  Present  Condition  of  Gold  Minin? 
in  the  Southern  Appalachian  States."  Transactions  A.  I.  M.  E.,  vof. 
XXV.,  1895,  p.  767. 

—  85  — 


in  the  schist  or  slates  "peters  out,"  the  miner  knows,  or 
should  know  that  by  cross-cutting  in  the  right  direction,, 
it  is  likely  that  another  lens  will  be  found,  which  overlaps 
the  first  in  longitudinal  extent.  The  tenor  of  the  Appa- 
lachian deposits  has  been  found  to  be  of  low  grade,  much 
lower  than  is  the  experience  in  the  Rocky  Alountains  or 
in  California.  It  is  another  thing,  however,  to  affirm  that 
veins  give  out.  The  Haile  Mine,  where  it  is  the  custom 
to  keep  development  work  some  years  ahead  of  the  mill ; 
the  Ducktown  copper  deposits,  and  the  zinc  deposits  at 
Franklin  Furnace,  are  hardly  examples  of  ore-deposits 
which  have  been  found  to  directly  peter  out. 

Sir  Archibald  Geikie,  in  his  "Founders  of  Geolog\'," 
says :  "If  geologists"  .  .  .  "could  only  be  brought  to 
realize  that  the  addition  of  another  paper  to  the  swollen 
flood  of  our  scientific  literature  involves  a  serious  respon- 
sibility," .  .  .  "how  greatly  would  they  conduce  to 
the  real  value  of  the  science  which  they  wish  to  serve." 
If  he  who  writes  a  paper  on  ore-deposits  takes  a  respon- 
sibility, ho^v  much  greater  is  the  load  assumed  by  him 
who  adds  to  his  own  remarks  promiscuous  citation  from 
the  great  body  of  past  literature,  in  support  of  this  or  that 
hypothesis.  Bearing  in  mind  that  unrelated  facts  are  in 
themselves  of  no  more  use  than  are  the  separate  parts  of  a 
steam  engine,  strewn  about  on  the  floor  of  a  building,  I 
still  maintain  that  authors  of  the  theories  of  ore-genesis, 
classifications  of  ore-deposits,  and  the  like,  should  found 
their  views  more  largely  on  the  results  of  their  own  obser- 
vations. Citations  from  previous  literature,  if  confined 
within  a  narrower  range,  dealing  with  those  occurrences 
of  ores  of  which  the  author  himself  has  been  a  witness^ 
serve  better  their  desired  end.  By  such  a  concentration 
of  literature  would  much  of  the  speculative  reasoning,  of 
doubtful  value,  be  eliminated  from  the  discussion  of  the 
interesting  science  of  ore-deposits.  While  not  question- 
ing the  fact  that  ^Ir.  Richard  Beck"  may  have  conscien- 
tiously recorded  the  results  of  his  observations  at  Bere- 
zovsk,  and  the  conclusions  drawn  therefrom,  I  am  in- 
clined to  question  the  value  of  Mr.  W.  H.  Weed's  cita- 


*^"Lehre  von  Erzlagerstatten,"  1891,  p.  324. 
—  86  — 


tion,"  thus  at  second  hand,  in  support  of  his  statements 
regarding  magmatic  quartz  veins. 

The  San  Juan  region  of  Colorado  has  been  quoted  to  a 
considerable  extent  by  writers  who  have  obtained  their 
information  by  other  means  than  direct  and  careful  ob- 
servation of  its  phenomena.  As  an  example,  Mr.  Spurr 
says:  "Prof.  Kemp  has  called  attention  to  the  San  Juan 
region  in  Colorado,  where  the  different  veins  have  been 
classified  by  T.  B.  Comstock  as  follows :  i.  The  northwest 
system  with  tetrahedrite.  2.  The  east  and  west  with  bis- 
muth, and  less  often  with  nickel  and  molybdenum. 
3.  The  northeast  with  tellurides  and  antimony,  and  sul- 
phur compounds  of  the  precious  metals. 

"The  same  writer  cites,  in  this  connection,  the  Telluride 
district  in  Colorado,  where  a  heavy  vein  is  cut  out  and 
faulted  by  a  later  one  of  different  metalliferous  char- 
acter." 

Referring  first  back  to  the  writings  of  Dr.  T.  B.  Com- 
stock," in  the  "Geology  and  Mineralogy  of  San  Juan 
County,  Colorado,"  I  find  that  the  above  generalizations 
were  made  on  certain  veins  occurring  in  a  small  area  of 
what  has  since  been  termed  the  Silverton  quadrangle  of 
the  United  States  geologic  atlas.  In  view  of  the  careful 
work  recently  done  in  that  area  by  Mr.  Ransome,  of  the 
United  States  Geological  Stfrvey,  Dr.  Comstock's  classifi- 
cation can  hardly  be  accepted  as  final.  In  the  second 
paper  of  Dr.  Comstock,"  "The  Geology  and  Vein-Struc- 
ture of  Southwestern  Colorado,"  he  very  reasonably 
states  that  "it  is  not  claimed  that  the  opinions  here  ex- 
pressed are  such  as  can  withstand  the  sifting  to  which 
other  years  of  inquiry  must  subject  them." 

Referring  next  to  the  writings  of  Prof.  Kemp,"  quoted 
by  Mr.  Spurr,  I  find  remarks  as  follows,  in  addition  to  the 
classifying  of  the  veins  above  noted:  "There  are  in  this 

*2  "A  further  Discussion  on  Ore  Deposits,"  Engineering  and  Mining 
Journal,  April  i8,  1903,  p.  595.    Also  vide  supra  p.  64. 

S3  T.  B.  Comstock,  "Geology  and  Mineralogy  of  San  Juan  County,  Colo- 
rado," Transactions  American  Institute  Mining  Engineers,  Vol,  XI,  1882,  p. 
189. 

**  "The  Geology  and  Vein-Structure  of  Southwestern  Colorado,"  TranS' 
actions  American   Inst'itute  Mining  Engineers,  vol.  xv.,    1886,  p.   256. 

3^J.  F.  Kemp,  "The  Role  of  the  Igneous  Rocks  in  the  Formation  of 
Veins,"  Transactions  American  Institute  Mining  Engineers,  Vol.  XXXI,  p. 
179.  Also,  "Ore  Deposits  of  the  United  States  and  Canada,"  New  York^ 
1900,   p.    288. 

—  87  — 


district  four  sets  of  fissures,  but  only  one  carries  the 
ores."  .  .  .  *'In  one  instance  thfe  Smuggler  vein  is 
faulted  by  the  Pandora,  a  later  vein  which  does  not  carry 
ores  sufficiently  rich  to  be  mined  profitably."  The  above 
statements  of  Prof.  Kemp  are,  as  he  states,  partly  inferred 
from  my  report  on  the  Telluride  quadrangle""'  of  the  San 
Juan  region.  But  it  seems  to  me  that  to  interpret  my 
conclusions  that  the  northwest  veins  of  the  Telluride 
quadrangle  are  the  more  important  ore-carriers  into  a 
statement  that  only  one  set  of  fissures  carries  the  ores,  is 
much  like  bending  a  fact  to  suit  a  hypothesis.  I  say 
nothing  in  regard  to  Prof.  Kemp's  conclusions,  I  object 
to  his  premises.  Again  the  work  on  which  my  repor^ 
was  based  was  done  in  1896,  and  I  was  limited  geo- 
graphically in  my  observations  so  as  not  to  include  the 
Camp  Bird  vein,  which  at  that  time  was  little  developed. 
Prof.  Kemp's  paper"  was  published  in  1901,  and  yet  he 
quotes  a  statement  of  m^ine  made  five  years  before  that 
the  Pandora  vein  carries  no  ore.  That  is  probably  true, 
in  the  Telluride  quadrangle.  If  i\Ir.  Ransome's  sugges- 
tion is  correct,  however,  and  I  believe  it  is,  that  the  Pan- 
dora and  Camp  Bird  are  an  identical  vein,  it  follows  that 
the  Pandora  in  the  Silverton  quadrangle  has  proven  sin- 
gularly productive  in  gold.  This  Prof.  Kemp  could  have 
satisfied  himself  of  had  he  been  at  the  pains  to  make  ob- 
servations for  himself  in  the  San  Juan.  As  it  was,  he  at- 
tempted to  support  a  speculation  in  regard  to  the  origin 
of  ores  by  the  general  application  of  a  statement  of  mine 
which  applied  and  was  intended  to  apply  only  to  a  portion 
of  the  district  under  consideration.  My  statement  was 
simply :  "No  remunerative  values  have,  so  far  as  has  been 
ascertained,  been  found  in  the  Pandora  vein."" 

I  have  shown  in  the  Telluride  report  that  there  is  good 
evidence  that  the  majority  of  the  veins  of  the  quadrangle 
were  formed  at  the  same  time,  and  from  Mr.  Ransome's 
statements  in  the  Silverton  bulletin"  it  is  plain  that  he 

"  "A  Preliminary  Report  on  the  Mining  Industries  of  the  Telluride  Quad- 
rangle, Colorado,"  i8th  Annual  Report  United  States  Geological  Survey,  pt. 
iii,  p.  745- 

^  "The  Role  of  the  Igneous  Rocks  in  the  Formation  of  Veins." 

*s  Op.  cit.  o,  834- 

» "A  Report  on  the  Economic  Geology  of  the  Silverton  Quadrangle, 
Colorado,  F.  C.  Ransome,  Bulletin  United  States  Geological  Survey,  182, 
1901,  pp.  56,  et  seq. 

—  88  — 


does  not  regard  a  well-defined  succession  of  ore  deposi- 
tion in  that  part  of  the  San  Juan  as  by  any  means  proven. 
As  for  the  contents  of  the  veins,  it  is  only  necessary  to 
refer  to  the  published  maps  of  the  Telluride  and  Silverton 
quadrangles,  and  to  look  at  the  lists  of  ore  and  gangue 
minerals  which  have  been  found  in  the  various  mines  to 
disprove  any  statements  that  veins  having  certain  direc- 
tions are  characterized  by  certain  minerals,  and  that  those 
running  at  angles  to  them  contain  different  minerals. 

The  San  Juan  region  of  Colorado  is  easily  accessible, 
and  all  are  at  liberty  to  make  such  observations  as  they 
see  fit  in  that  classic  laboratory  of  ore  deposition.  Those 
investigators  who  desire  to  make  use  of  its  phenomena  in 
support  of  their  views  should  avail  themselves  of  an  op- 
portunity to  visit  the  mines  in  person,  rather  than  to  quote, 
at  second  and  third  hand,  observations  which  must  have 
more  or  less  of  temporary  value  in  a  district  which  is  so 
rapidly  undergoing  development. 

The  thorough  and  painstaking  work  of  Mr.  F.  L.  Ran- 
some  on  the  Silverton  quadrangle  can  perhaps  best  be 
appreciated  by  those  who  have  had  experience  in  that 
part  of  the  country.  In  summing  up  his  observations  on 
the  fissures  he  says:  "While  many  of  the  fissures  in  the 
Silverton  quadrangle,  including  some  which  differ  widely 
in  direction,  were  formed  at  substantially  the  same  time, 
there  have  been  later  periods  of  Assuring,  also  followed 
by  vein  deposition."  .  .  .  "This  generalization,  how- 
ever, should  not  be  taken  too  rigidly,  as  it  is  very  probable 
whenever  a  prominent  set  of  nearly  parallel  fissures  were 
formed,  other  fissures  intersecting  the  dominant  set  at 
various  angles  were  produced  at  the  same  time." 

The  above  quotation  exhibits  the  moderation  of  state- 
ment characteristic  of  the  conscientious  observer,  and 
partakes  neither  of  the  dogmatic  certainty  of  the  library 
theorist  nor  the  hasty  generalization  of  the  geologist  on 
horseback.  To  offer  harsh  criticism  in  the  course  of  dis- 
cussion of  a  subject  so  freshly  explored  as  that  of  the  dis- 
tribution and  genesis  of  ores  is  both  unwise  and  unjus- 
tifiable. I  make  bold  to  suggest,  however,  that  there  are 
different  ways  of  studying  ore-deposits.     To  march  has- 

—  89  — 


tily  through  a  mine  drift,  and  to  scramble  into  a  few 
show-off  stopes  under  the  necessarily  hurried  guidance 
of  the  mine  foreman  or  shift  boss ;  to  visit  one  or  two  of 
the  principal  mines  of  a  district  in  company  with  a  large 
party  whose  ideas  are  for  the  most  part  preconceived  or 
directed  at  the  time  by  the  temporary  bias  of  one  leading 
intellect ;  that  is  one  thing.  It  is  another  thing  to  return 
alone,  day  after  day,  to  the  many  workings  of  a  great 
mine ;  to  scan,  by  the  light  of  a  single  candle,  the  momen- 
tous problems  of  vein  phenomena.  While  not  wishing  to 
put  muscular  geology  into  the  foreground,  I  maintain 
that  he  who  climbs  thousands  of  feet,  over  snow  and  rock 
slides,  to  an  abandoned  prospect,  in  order  to  determine 
points  ill  understood,  may  speak  with  more  authority  than 
he  who  contemplates  the  view  from  the  beaten  trail.  The 
silent  peak,  where  human  environment  no  longer  in- 
trudes, affords  a  better  vantage  point  for  accurate  gaug- 
ing of  the  diagram  of  nature  than  does  the  rear  platform 
of  an  observation  car. 

It  appears  excusable  for  one  whose  views  have  been 
attained  in  field  work,  frequently  in  regions  hostile  to 
human  control,  to  protest  when  he  finds  subsequent  in- 
vestigators disregarding  or  misinterpreting  his  observa- 
tions, ballasting  the  literature  of  ore-deposits  with  high- 
worded  theories,  and  building  hypotheses  on  unverified 
statements  relating  to  parts  of  the  world  which  they  have 
never  seen. 


90  — 


REPLY  TO  FOREGOING/ 

BY  JAS.   F.   KEMP. 

Mr.  Purington  places  before  American  readers  many 
observations  made  in  Siberia  and  other  parts  of  the  world 
which  are  of  great  value  and  which  are  extremely  sug- 
gestive. The  association  of  gold  with  basic  igneous  rocks 
and  its  genetic  connection  with  basic  intrusives,  even 
when  it  is  found  in  silicious  walls,  will  tend  to  stimulate 
observation  and  reflection.  These  relations  have  also  an 
important  bearing  in  a  general  way  upon  the  genetic  con- 
nection between  eruptive  rocks  and  ore  formation  and  will 
unquestionably  be  carefully  pondered  by  all  who  follow 
the  discussion  now  in  progress.  At  the  same  time,  the 
almost  universal  association  of  gold  with  quartz,  the  ap- 
parently well  authenticated  cases  of  its  occurrence  as  an 
original  mineral  in  acidic  rocks,  which  have  been  de- 
scribed by  Moericke,  G.  P.  Merrill,  Spurr  and  others, 
niake  one  conservative  about  a  too  prompt  surrender  of 
the  latter  view. 

On  page  y}^,  Mr.  Purington  finds  some  ambiguity  in  my 
use  of  the  term  pegmatite  with  the  almost  tacit  assump- 
tion, on  my  part  that  the  pegmatites  occur  in  veins,  or,  as 
many  think,  in  dikes.  When-  one  learns  from  the  subse- 
quent text  that  Mr.  Purington's  conception  of  the  typical 
pegmatite  is  that  the  latter  forms  a  localized  and  coarsely 
crystalline  phase  of  an  otherwise  normal  eruptive  mass, 
as  against  an  occurrence  in  veins  or  dikes,  believed  by  him 
to  be  exceptional,  this  supposed  ambiguity  is  not  surpris- 
ing. 

Nevertheless  I  am  convinced  that  the  sense  in  which  I 
used  the  word  is  the  one  generally  held  by  geologists  and 
especially  by  petrographers ;  that  the  vast  majority  of  the 
pegmatites  which  have  been  studied,  occur  in  fissures  in 

iFrom  the  Engineering  and  Mining  Journal,  of  September  12, 1903. 
—  91  — 


walls  of  a  different  rock ;  that  they  present  entirely  analo- 
gous phenomena  to  ordinary  veing;  and,  in  connection 
with  the  study  of  the  latter  they  are  of  significance  all  too 
slightly  appreciate. 

Mr.  Philip  Argall's  observations  in  Gilpin  and  Clear 
Creek  counties  tally  perfectly  with  iny  own  in  the  same 
region.  There  are  hundreds,  it  may  be  thousands,  of  these 
veins  cutting  not  only  granite,  but  dark  gneisses  as  well. 
The  observations  of  Mr.  H.  Kilbum.  Scott  in  Brazil,  which 
Mr.  Purington  cites,  can  also  be  fully  corroborated  upon 
Manhattan  Island,  where,  for  example,  we  have  pegma- 
tites of  all  widths  up  to  12  or  15  ft.  cutting  mica  schists, 
gneisses  and  crystalline  dolomites  indifferently.  In  most 
beautiful  and  instructive  fashion,  they  illustrate  nearly  all 
the  phenomena  of  veins,  such  as  banded  veins,  blind  veins, 
bed-veins,  punching  and  offsetting  veins,  variations  in 
vein  filling  and  gradations  from  granitic  mixtures  up  to 
those  which  are  largely,  if  not  almost  entirely,  quartz. 

Now  the  question  of  the  nature  of  pegmatites  has  been 
one  of  the  most  interesting  of  those  which  have  been  de- 
bated during  the  last  twenty  or  thirty  years.  Some  ob- 
servers have  urged  that  they  are  essentially  igneous,  hav- 
ing cooled  from  fusion,  albeit  in  association  with  abnor- 
mal quantities  of  steam  or  other  mineralizers.  Others 
have  urged  their  essential  nature  as  veins  and  have  placed 
emphasis  upon  the  part  played  by  solution  at  high  tem- 
peratures. 

Of  course,  a  discussion  of  this  sort  could  only  center 
around  those  pegmatites  which  have  filled  fissures  in  rocks 
of  a  different  nature.  If  the  pegmatite  forms  a  local  phase 
in  an  eruptive  mass,  it  is  essentially  eruptive  like  the  rest. 
One  only  needs  to  refer  to  the  three  or  four  principal 
papers  upon  them  to  discover  the  currency  and  correct- 
ness of  the  usage  employed  by  me.  Thus  in  the  con- 
tributions of  Crosby  and  Fuller^  and  of  George  H.  Will- 
iams,^ which  are  the  two  best  known  in  America  treating 
of  this  subject,  picture  after  picture  is  given  in  illustration 

^W.  O.  Crosby  and  M.  L.  Fuller,  "Origin  of  Pegmatite,"  American  Geolo- 
gist, March,  1897.  The  paper  is  reprinted  from  the  Technology  Quarterly, 
December,  1896. 

2Q.  H.  Williams,  "General  Relations  of  the  Granitic  Eocks  in  the  Middle 
Atlantic  Piedmont  Plateau,'  15th,  Ann.  Rep.  U.  b.  Geol.  burvej,  675. 


of  the  text,  yet  they  all  exhibit  veins  (or  dikes).  In  fact 
the  very  title  of  the  most  important  mineralogical  mono- 
graph of  recent  years  is  "Die  Syenitpegmatitgange  der 
Siidnorwegischen  Augit-und  Nephelinsyenite."  (The 
syenitic  pegmatite  dikes  of  the  augite  and  nepheline 
syenites  of  southern  Norway.)  In  it  Professor  Broegger 
concludes  that  the  pegmatites  are  igneous  phenomena,  but 
that  they  occur  otherwise  than  in  "Gauge,"  which  word  is 
used  in  German  indifferently  for  dikes  and  veins,  never 
seems  to  suggest  itself. 

I  do  not  wish  to  urge  this  matter  unduly,  for  the  differ- 
ence of  conception  may  not  seem  to  be  of  vital  importance, 
but  it  is  regarding  these  very  points  of  inaccurate  knowl- 
edge or  half-knowledge  that  Mr.  Purington  in  various 
places  expresses  himself  in  terms  of  the  most  caustic 
criticism  of  other  unfortunates,  whereas  a*  fellow-feeling 
should  make  him  more  "wondrous  kind." 

Toward  the  close  of  his  paper  Mr.  Purington  takes  me 
somewhat  severely  to  task  for  certain  citations  believed 
by  him  to  have  been  loosely  or  inaccurately  made,  and  to 
furnish  a  text  for  a  short  homily  with  whose  general  doc- 
trines only  a  person  of  most  abandoned  depravity  could 
fail  to  agree.  There  appears  to  be  some  reason  for  Mr. 
Purington's  criticisms  even  though  they. impress  me  as  a 
large  funeral  over  a  small  baby,  and  I  cannot  but  express 
my  gratification  at  the  opportunity  to  clear  away  any  mis- 
conceptions or  mistakes.  The  circumstances  when  briefly 
stated  are  as  follows : 

Mr.  Spurr,  writing,  as  I  believe,  in  Turkey  and  away 
from  original  sources  of  reference,  cited  my  citations 
on  the  San  Juan  region  of  Colorado,  as  given  in  the 
"Ore  Deposits  of  the  United  States  and  Canada."  These 
citations  are  quite  fully  reproduced  by  Mr.  Purington  and 
need  not  be  repeated  here.  I  will  only  say  that  I  have 
again  read  them  in  the  text-book  referred  to;  and  while 
they  are  condensed  and  brief,  they  are,  I  believe,  correctly 
given,  and  being  in  a  text-book  which  aims  to  give  a  con- 
spectus of  the  literature,  the  citations  are  not  only  proper 
but  inevitable. 

At  the  time  that  both  the  "Ore  Deposits"  and  the  paper 


—  93 


on  the  "Role  of  the  Igneous  Rocks,  etc.,"  were  prepared 
and  printed,  M^.  Ransome's  bulletin  on  the  Silverton 
quadrangle  had  not  been  seen  by  me,  nor  did  I  know  of  its 
existence.  The  time  of  the  issue  is  not  very  different  from 
that  of  the  ''Role,  etc.,"  but  the  manuscript  of  the  "Ore 
Deposits"  was  prepared  the  previous  year.  I  therefore 
dismiss  Mr.  Ransome's  paper  from  the  discussion. 

That  I  have  not  yet  had  the  privilege  of  visiting  the 
San  Juan,  as  Mr.  Purington  remarks,  is  a  serious  dis- 
advantage, but  he  does  not  seem  to  fully  appreciate  that 
the  demands  upon  the  time  and  strength  of  one  who 
teaches  in  a  university  are  exacting;  that  the  attractive 
and  important  mining  districts  of  North  America  are  nu- 
merous ;  and  that  when  these  districts  have  been  carefully 
studied  and  described  by  competent  obser\^ers  it  is  the 
natural  disposition  of  the  teacher  to  devote  a  part  of  his 
vacation  to  breaking  away  into  regions  less  fully  inves- 
tigated. I  hope  that  at  some  future  day,  however,  the 
long  cherished  hope  of  visiting  the  San  Juan  may  be 
realized. 

I  cannot  forbear  expressing  a  word  of  praise  of  the 
careful  methods  of  field-work  with  which  Mr.  Purington 
gathered  his  observations  far  up  the  steep  talus  slopes  and 
in  the  lonely  drifts,  for,  although  these  are  the  methods 
of  every  conscientious  mining  engineer  and  of  every  geol- 
ogist who  is  worth  his  salt,  yet  the  San  Juan  is  a  precipi- 
tous and  difficult  country  for  their  application. 

In  the  paper  on  the  "Role  of  the  Igneous  Rocks,  etc.," 
in  one  place  I  was  endeavoring  to  show  that  where  several 
sets  of  different  veins  are  found  in  a  district  and  have  con- 
trasted vein-filling,  they  are  difficult  to  explain  by  the 
hypothesis  of  lateral  secretion  even  in  its  extended  sense. 
The  passage  which  is  the  main  cause  of  Mr.  Purington's 
criticism  is  as  follows : 

"The  Sequence  of  Vein-Formations. — There  are  also 
cases  of  successive  and  constrasted  vein-formation.  More 
than  fifteen  years  ago  R.  C.  Hills  recognized  three  sets  of 
veins  in  the  San  Juan  region  of  Colorado,  each  with  dif- 
ferent ores;  and  the  recent  work  on  the  Telluride  quad- 
rangle of  the  U.  S.  Geological  Survey  has  shown  in  detail 


many  of  the  structural  relations.^  There  are  in  this  dis- 
trict four  sets  of  fissures,  but  only  one  carries  the  ores — 
a  remarkable  state  of  things  if  the  ores  are  due  to  the  uni- 
versal circulation  of  the  groundwater.  In  one  instance, 
the  Smuggler  vein  is  faulted  by  the  Pandora,  a  later  vein 
which  does  not  carry  ores  sufficiently  rich  to  be  mined 
profitably." 

The  subsequent  comments  given  in  the  next  paragraph 
but  one,  upon  this  and  other  illustrations,  so  far  from 
being  extravagant,  seem  to  me  after  the  lapse  of  two  years 
to  be  exceptionally  temperate  and  guarded. 

In  the  passage  above  quoted  there  seems  to  be  no  doubt 
that  the  phenomena  cited  by  Mr.  Hills  are  in  the  San  Juan 
region  and  really  exist,  and  are  pertinent  to  my  argument. 
The  reference  to  Mr.  Purington's  paper  is  based  especially 
upon  the  following  passages  on  page  767.  After  setting 
forth  the  compass  bearings  of  the  fissures,  he  states: 
''From  the  foregoing  it  is  evident  that  there  are  four  gen- 
eral directions  of  fissuring,  (i)  east  and  west,  (2)  north- 
east, best  developed  in  the  central  and  southeastern  por- 
tions of  the  quadrangle,  and  (3)  north  and  south,  and 
(4)  northwesterly,  best  exemplified  in  the  northeastern 
portion." 

A  few  lines  above  this  paragraph,  in  speaking  in  detail 
of  the  fourth  or  northwesterly  group  of  fissures,  he  states, 
"This  group  is  of  the  most  interest  from  an  economic 
standpoint  as  will  be  set  forth  under  the  heading  'The 
Veins.' "  Thus  it  is  evident  that  when  I  stated  that  in  the 
Telluride  quadrangle  there  were  "four  sets  of  fissures,  but 
only  one  carried  the  ores,"  my  statements  were  too  sweep- 
ing and  were  loose  and  inaccurate,  because  in  other  por- 
tions of  the  quadrangle  others  of  the  fissures  than  the 
northwestern  series  are  the  basis  of  some  of  the  less  im- 
portant mines,  as  Mr.  Puring^on's  paper  makes  clear. 

The  Smuggler  and  two  or  three  parallel  veins  are 
faulted  by  the  Pandora,  and  the  ore  in  the  Pandora  is 
different  from  the  ores  in  the  thrown  veins  as  Mr.  Pur- 
ington  states  on  page  779.  My  remark  about  the  Pandora 
was  that  it  "does  not  carry  ores  sufficiently  rich  to  be 

»See  C.   W.  Purington,  18th  Ann.  Rep.  V.  8.  Geol.  Surv.,  Part  iii,  p.  745. 
—  9S  — 


mined  profitably."  Mr.  Purington's  words  on  page  834 
are,  "No  remunerative  values  have,' so  far  as  has  been 
ascertained,  been  found  in  the  Pandora  vein." 

I  trust  that  in  this  statement  I  have  made  such  acknowl- 
edgment as  the  instance  demands,  for  I  am  anxious  to  do 
so  amply.  Nevertheless,  with  the  correction  rigidly  ap- 
plied, the  case  will  furnish  an  excellent  and  perfectly 
justifiable  illustration  of  the  point  for  which  it  was  first 
employed.  We  have  four  great  series  of  fissures  with 
the  greater  number  of  productive  mines  and  practically 
all  those  in  the  northeastern  portion  of  a  large  quadrangle, 
along  one  set.  A  later,  and*  so  far  as  was  known  at  the 
time,  an  unremunerative  vein,  the  Pandora,  faults  the 
Smuggler,  which  is  older  and  which  has  been  very  pro- 
ductive. Even  if,  in  an  adjacent  quadrangle  and  two 
miles  away,  as  has  been  suggested  by  Air.  Ransome,  the 
very  rich  Camp  Bird  mine  is  on  the  Pandora  fissure,  the 
case  is  not  essentially  altered  for  the  purpose  for  which 
I  used  it,  and  I  repeat  that  m»y  remarks  upon  it  and  upon 
others  of  similar  nature  were  temperate  and  guarded. 

The  gist  of  the  whole  matter  turns,  .however,  upon  the 
use  of  citations,  and  aga^inst  the  practice  Mr.  Purington 
directs  his  heaviest  attack.  But  it  seems  to  me  that  in  this, 
as  in  most  other  matters,  good  common  sense  should  be 
exercised.  If  a  writer  were  at  this  day  to  advance  some 
such  "high-worded"  theory  as  that  the  influence  of  the 
moon  was  potent  in  the  formation  of  ore-deposits,  and 
were  to  support  it  by  citations  from  the  writers  of  Agri- 
cola's  time  or  earlier,  he  would  be  open  to  deserved  cen- 
sure. But  if,  on  the  other  hand,  he  were  to  present  a 
sane  and  temperate  thesis  or  were  emphasizing  certain 
aspects  of  a  discussion — said  aspects  not  being  appreciated 
at  their  proper  importance  by  the  contributions  most  read 
and  trusted  at  the  time — he  would  be  perfectly  justified 
in  citing  in  his  support  the  observations  of  any  or  all  of 
those  mining  engineers  and  geologists  who  are  known  to 
be  careful  and  accurate  in  their  work.  Among  the  papers 
contributed  by  such  observers  there  is  none  in  my  opinion 
which  deserves  quotation  more  than  Mr.  Purington's  re- 
port upon  the  Telluride  quadrangle.    In  my  view  it  is  not 

-96- 


prohibitive  if  the  citer  has  not  visited  the  region  studied 
by  the  "citee,"  the  force  of  the  reference  depending  upon 
the  reputation  of  the  latter  and  the  appropriateness  of  the 
case.  I  will  not  hesitate  to  maintain — always  provided 
the  thesis  is  reasonable — that  it  is  the  citer's  duty  to  bring 
out  the  cases  in  order  to  properly  present  the  full  evidence 
to  his  readers,  and  to  show  that  he  has  made  his  paper 
a  subject  of  thorough  and  exact  scholarship.  Even  Mr. 
Purington  himself  cannot  refrain  from  using  such  cita- 
tions when  they  fortify  his  point,  as  the  Demerara  in- 
stance, page  83,  illustrates. 

I  submit  in  closing,  therefore,  that  except  so  far  as 
Mr.  Purington  has  a  case  against  me  of  somewhat  loose 
quotation  of  his  paper,  which  I  do  not  hesitate  to  acknowl- 
edge and  regret,  there  is  but  limited  force  in  his  closing 
paragraphs. 


.97. 


ORE    DRESSING 

By  ROBERT  H.  RICHARDS 

This  magnificent  contribution  to  metallurgical  literature  is 
now  ready,  after  many  years  of  careful  preparation  by  the  author, 
who  is  one  of  the  ablest  experts  on  the  question.  In  this  ex- 
cellent treatise  the  ore  dressing  theory  is  thoroughly  developed, 
and  an  inexhaustible  mine  of  useful  facts  and  practical  experi- 
ments is  brought  forth  that  virtually  outrivals  any  other  work 
ever  before  issued  on  any  branch  of  mechanical  and  metallurgical 
engineering.  The  unswerving  aim  of  the  author  has  been  to  elu- 
cidate to  the  working  student  modern  American  practice,  referring 
for  comparison  to  European,  and  to  so  expound  the  principles 
of  the  art  as  at  present  understood  as  to  make  advance  easy  in 
the  future.  The  plan  of  the  book  is  essentially  practical,  and  is 
divided  into  four  main  parts,  viz.:  Crushing,  Separating,  Con- 
centrating and  Washing,  Accessory  Apparatus  and  Mill  Process, 
and  Management.  The  numerous  subdivisions  include  elaborate 
chapters  on  Gravity  Stamps,  Screen  Sizing  and  its  Principles, 
Classifiers,  Hand  Picking,  Jigs  and  Laws  of  Jigging,  Slime  Con- 
centration and  Amalgamation. 

This  superb  work  is  beyond  all  doubt  or  question  a  veritable 
masterpiece  of  technical  literature,  and  should  occupy  a  promi- 
nent place  in  every  industrial  library.  Mining,  metallurgical  and 
mechanical  engineers  cannot  afford  to  be  without  it,  as  it  is 
specifically  the  kind  of  literature  the  profession  nowadays  demand 
as  an  infallible  guide  to  practical  work.  > 

Chapter  I. — General  Principles.  Chapter  XIII. — Hand  Picking. 

Part  I.— Breaking,    Crushing    and  Chapter  XIV.— Jigs. 

Chapte^n!— PreUminary  Crushing.  Chapter  XV.— Laws  of  Jigging. 

Chapter  III.— Rolls.                    _  Chapter  XVI.— Fine  Sand  and  Slime 

Chapter  IV. — Steam,  Pneumatic  and  Concentrators. 

Spring  Stamps  Chapter  XVII.— Amalgamation. 
Chapter  V. — Gravity  Stamps.  ^,       .       -v-frTTT      nr-      n                t^ 
Chapter  VI.— Pulverizers  other  than  Chapter  XVIII.— Miscellaneous  Pro- 
Gravity  Stamps.  cess  of  Separation. 
Chapter  VII. — Laws  of  Crushing.  Part  III. — Accessory  Apparatus: 
Part  II. — Separating,  Concentrating  Chapter  XIX. — Accessory  Apparatus, 
or  Washing:  Part    IV. — Mill  Processes  and  Man- 
Chapter  VIII. — Preliminary  Washers.  agement : 

Chapter  IX. — Sizing  Screens.  Chapter  XX. —  Summary    of  Princi- 

Chapter     X. —  Principles    of    Screen  pies  and  Outlines  of  Mills. 

Sizing.  Chapter  XXI.  —  General     Ideas     on 

Chapter  XI. — Classifiers.  Milling. 

Chapter  XII. — Laws  of  Classifying  by  Appendix,  Tables  and  Other    Useful 

Free  Settling  in  Watsr.  Information.     Index. 

Two  Volumes.    Octavo,  Cloth.     J250  Pages,  profusely  illustrated. 

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